Decide how to manage simp-core in puppetsyncs

[op-ct]

Currently, if simp-core is included in a puppetsync repolist, it is treated as a pupmod, which is probably the least significant aspect of its purpose. As a result, syncs will add a number of pupmod-specific file that are not be appropriate for simp-core's larger purpose (as seen in #875).

We need to decide how and what to handle for simp-core during puppetsyncs. It is reasonable to sync some assets (like LICENSE), but others will necessarily remain unique.