Added extended addon script helpers

[Kit Authoring Improvements]

* Added print_addon_descriptions and run_extended_addon helpers to
  support extended addon scripts.

  Rather than have all the addons in the `hooks/addon` file, you can add
  individual `hook/addon-<name>~<shortcut>`.  To do so, you need to
  follow the following conventions:

  * The script gets passed as its first argument the action to take.
    This is either help or run.  Help prints out the description to be
    used in list, and run causes the script to run.

  * The main hooks/addon script must use print_addon_descriptions in its
    list command block, with alternative arguments of the base commands
    and descriptions.  Example:

    ```
    list) print_addon_descriptions \
            "command" "description of command" \
            "another" "description of another command" ;;
    ```

  * The main hook/addon script uses run_extended_addon as its catch-all
    `*)` block.

lib/Genesis/Helpers.pm

@@ -60,6 +60,13 @@ describe() {
 }
 export -f describe
 
+titleize() {
+	if [[ $# -gt 0 ]] ; then
+		echo "$@" | /usr/bin/perl -e "while (<STDIN>) { s/([\\w']+)/\\u\\L\$1/g; print }"
+	fi
+}
+export -f titleize
+
 humanize_path() {
   /usr/bin/perl -I$GENESIS_LIB -MGenesis -e 'binmode STDOUT, ":encoding(UTF-8)"; print humanize_path("$ARGV[0]")' "$1"
 }
@@ -743,3 +750,59 @@ version_check() {
   return 0
 }
 export -f version_check
+
+# Support for extended addon hook scripts
+if [[ "$GENESIS_KIT_HOOK" == "addon" ]] ; then
+	print_addon_descriptions() {
+
+		local label short msg
+		describe "The following addons are defined for the #C{$GENESIS_KIT_ID} kit:"
+		while [[ "$#" -gt 0 ]]; do
+			label="$(echo "$1" | sed -e 's/\([^~]*\).*/\1/')"
+			short="$(echo "$1" | sed -e 's/\([^~]*\)\(~\(.*\)\)\{0,1\}/\3/')"
+			[[ -n "$short" ]] && short="|$short"
+			describe "" "  #Gu{$label$short}" "$(echo "$2" | sed -e 's/^/    /')"
+			shift 2;
+		done
+		(
+			shopt -s nullglob
+			for addon in hooks/addon-*; do
+				[[ -x "$addon" ]] || chmod +x "$addon"
+				msg="$($addon help | sed -e 's/^/    /')" || continue
+				label="$(echo "$addon" | sed -e 's/.*\/addon-\([^~]*\).*/\1/')"
+				short="$(echo "$addon" | sed -e 's/.*\/addon-\([^~]*\)\(~\(.*\)\)\{0,1\}/\3/')"
+				[[ -n "$short" ]] && short="|$short"
+				describe "" "  #Gu{$label$short}" "$msg"
+			done
+		)
+		echo ""
+	}
+	export -f print_addon_descriptions
+
+	run_extended_addon() {
+		addon=
+		if [[ -f "hooks/addon-$GENESIS_ADDON_SCRIPT" ]] ; then
+			addon="hooks/addon-$GENESIS_ADDON_SCRIPT"
+		else
+			addon="$(compgen -G "hooks/addon-$GENESIS_ADDON_SCRIPT"'~*')"
+			if [[ -z "$addon" ]] ; then
+				addon="$(compgen -G 'hooks/addon-*~'"$GENESIS_ADDON_SCRIPT")"
+				if [[ -n "$addon" ]] ; then
+					label="$(echo "$addon" | sed -e 's/.*\/addon-\([^~]*\).*/\1/')"
+					describe >&2 "Running #G{$label ($GENESIS_ADDON_SCRIPT)} addon for #C{$GENESIS_ENVIRONMENT} #M{$GENESIS_KIT_NAME} deployment"
+				fi
+			fi
+		fi
+
+		if [[ -n "$addon" && -f "$addon" ]] ; then
+			[[ -x "$addon" ]] || chmod +x "$addon"
+			"$addon" run "$@"
+			exit $?
+		else
+			echo "Unrecognized $(titleize $GENESIS_KIT_NAME) Genesis Kit addon."
+			list
+			exit 1
+		fi
+	}
+	export -f run_extended_addon
+fi