build target platform sources site (for use with TP and PDE Source Lookup)

So that dev and qe can use Fred's PDE source lookup tool [1] to grab source bundles on demand (instead of having to build a target platform locally w/ all the sources [2]), we need to:

[1] https://github.com/fbricon/pde.source.lookup/
[2] https://github.com/jbosstools/jbosstools-devdoc/blob/master/building/target_platforms/target_platforms_for_consumers.adoc#build-target-platform-bootstrapped-from-zip

• build a targetplatform with all the sources
• split that repo into two pieces: all the .source files, and everything else
• regen the metadata (featureandbundlepublisher) in each new repo so that all the features/plugins are uncategorized

OR...

• build a targetplatform without the sources
• transform the .target file so that each IU ends with .source
• build the target platform repo from the new .target file
• verify that sources repo includes the sources of nested features, and those features' plugins' sources too

Then once we have the targetplatform.source repo, publish that and verify it works with the PDE Source Lookup plugin:

1. install the PDE source lookup plugin
2. Window > Prefs > Update > Avail Software Sites > Add the new tp.source site
3. for something you want sources, use the plugin and see if it can resolve soources

Then, if that works, we can consider adding the new tp.source site into the JBT/devstudio composite sites, along with jbt + tp + central + central tp (or ds + ds tp + central + central tp) as a 5th child site.