Migrate CouchDB to rebar3

1. Change `src` to `apps` and all symlinks: In order to use the
local plugins `rebar3 ic setup_eunit [-f]`, we need to use correct
umbrella project structure. See erlang/rebar3#2729

2. Use `configure` script instead of `rebar.config.script` to download
dependencies: `make eunit` will get dependency cycle error if using
`rebar.config.script`

3. rebar3 has no options such as `skip_deps` or `-r`, so they were removed.

<!-- If your changes affects multiple components in different
     repositories please put links to those issues or pull requests here.  -->

- [x] Code is written and works correctly
- [x] Changes are covered by tests
- [ ] Any new configurable parameters are documented in `rel/overlay/etc/default.ini`
- [ ] A PR for documentation changes has been made in https://github.com/apache/couchdb-documentation

.formatter.exs

@@ -2,7 +2,7 @@
 [
   inputs: [
     "{mix,.formatter}.exs",
-    "{config,src}/*/test/exunit/*.{ex,exs}"
+    "{config,apps}/*/test/exunit/*.{ex,exs}"
   ],
   line_length: 90,
   rename_deprecated_at: "1.5.0"

.gitignore

@@ -39,94 +39,109 @@ rel/tmpdata
 share/server/main-coffee.js
 share/server/main.js
 share/www
-src/b64url/
-src/bear/
-src/certifi/
-src/config/
-src/couch/priv/couch_js/**/config.h
-src/couch/priv/couchjs
-src/couch/priv/couchspawnkillable
-src/couch/priv/couch_ejson_compare/couch_ejson_compare.d
-src/couch/priv/couch_js/**/*.d
-src/couch/priv/icu_driver/couch_icu_driver.d
-src/mango/src/mango_cursor_text.nocompile
-src/docs/
-src/ets_lru/
-src/excoveralls/
-src/fauxton/
-src/folsom/
-src/hackney/
-src/hqueue/
-src/hyper/
-src/ibrowse/
-src/idna/
-src/jiffy/
-src/khash/
-src/meck/
-src/metrics/
-src/mimerl/
-src/mochiweb/
-src/oauth/
-src/parse_trans/
-src/proper/
-src/rebar/
-src/recon/
-src/snappy/
-src/ssl_verify_fun/
-src/triq/
-src/unicode_util_compat/
-src/file_system/
-src/rebar3/
-src/erlfmt/
+apps/b64url/
+apps/bear/
+apps/certifi/
+apps/config/
+apps/couch/priv/couch_js/**/config.h
+apps/couch/priv/couchjs
+apps/couch/priv/couchspawnkillable
+apps/couch/priv/couch_ejson_compare/couch_ejson_compare.d
+apps/couch/priv/couch_js/**/*.d
+apps/couch/priv/icu_driver/couch_icu_driver.d
+apps/mango/src/mango_cursor_text.nocompile
+apps/docs/
+apps/ets_lru/
+apps/excoveralls/
+apps/fauxton/
+apps/folsom/
+apps/hackney/
+apps/hyper/
+apps/ibrowse/
+apps/idna/
+apps/jiffy/
+apps/khash/
+apps/meck/
+apps/metrics/
+apps/mimerl/
+apps/mochiweb/
+apps/oauth/
+apps/parse_trans/
+apps/proper/
+apps/rebar/
+apps/recon/
+apps/snappy/
+apps/ssl_verify_fun/
+apps/triq/
+apps/unicode_util_compat/
+apps/file_system/
+apps/rebar3/
+apps/erlfmt/
 tmp/
 
-src/couch/*.o
-src/couch/*.so
-src/couch/ebin/
-src/couch/priv/couch_js/config.h
-src/couch/priv/couchjs
-src/couch/priv/couchspawnkillable
-src/couch/priv/*.exp
-src/couch/priv/*.lib
-src/couch/priv/*.dll
-src/couch/priv/*.exe
-src/couch/vc120.pdb
-src/couch_epi/ebin
-src/couch_epi/erl_crash.dump
-src/couch_event/deps/
-src/couch_event/ebin/
-src/couch_index/ebin
-src/couch_log/ebin
-src/couch_peruser/doc
-src/couch_peruser/ebin
-src/couch_peruser/deps
-src/couch_peruser/couchperuser-*
-src/couch_peruser/erl_crash.dump
-src/couch_peruser/TEST-*.xml
-src/couch_peruser/*.beam
-src/couch_replicator/*.beam
-src/couch_replicator/ebin/replicator.app
-src/couch_replicator/.DS_Store
-src/couch_stats/*~
-src/couch_stats/*.beam
-src/couch_stats/deps
-src/couch_stats/ebin
-src/couch_stats/doc
-src/couch_stats/.project
-src/couch_tests/*.o
-src/couch_tests/*.so
-src/couch_tests/ebin/
-src/global_changes/ebin/
-src/mango/ebin/
-src/mango/test/*.pyc
-src/mango/nosetests.xml
-src/mango/venv/
-src/jwtf/.rebar3/
+apps/couch/*.o
+apps/couch/*.so
+apps/couch/ebin/
+apps/couch/priv/couch_js/config.h
+apps/couch/priv/couchjs
+apps/couch/priv/couchspawnkillable
+apps/couch/priv/*.exp
+apps/couch/priv/*.lib
+apps/couch/priv/*.dll
+apps/couch/priv/*.exe
+apps/couch/vc120.pdb
+apps/couch_epi/ebin
+apps/couch_epi/erl_crash.dump
+apps/couch_event/deps/
+apps/couch_event/ebin/
+apps/couch_index/ebin
+apps/couch_log/ebin
+apps/couch_peruser/doc
+apps/couch_peruser/ebin
+apps/couch_peruser/deps
+apps/couch_peruser/couchperuser-*
+apps/couch_peruser/erl_crash.dump
+apps/couch_peruser/TEST-*.xml
+apps/couch_peruser/*.beam
+apps/couch_replicator/*.beam
+apps/couch_replicator/ebin/replicator.app
+apps/couch_replicator/.DS_Store
+apps/couch_stats/*~
+apps/couch_stats/*.beam
+apps/couch_stats/deps
+apps/couch_stats/ebin
+apps/couch_stats/doc
+apps/couch_stats/.project
+apps/couch_tests/*.o
+apps/couch_tests/*.so
+apps/couch_tests/ebin/
+apps/global_changes/ebin/
+apps/mango/ebin/
+apps/mango/test/*.pyc
+apps/mango/nosetests.xml
+apps/mango/venv/
+apps/jwtf/.rebar3/
 test/javascript/junit.xml
 
 /_build/
-/src/bunt
-/src/credo/
-/src/httpotion/
-/src/jason/
-/src/junit_formatter/
+/apps/bunt
+/apps/credo/
+/apps/httpotion/
+/apps/jason/
+/apps/junit_formatter/
+
+.idea
+_build
+apps/bbmustache/
+apps/cf/
+apps/cth_readable/
+apps/erlware_commons/
+apps/eunit_formatters/
+apps/getopt/
+apps/providers/
+apps/relx/
+*.log
+rebar3.crashdump
+*.lock
+*.orig
+*.iml