Include all .ts files from referenced projects when building

Only problem now is how to deduplicate resources. i.e. when you have a
bower_components per project, how do you not duplicate the dependent project's
dependencies that you're also dependent on?
Add exported source folder setting to build path

This solves the problem of duplicate dependencies. :) Now you can just set only
your source folder to be exported.

Potential problem (that hasn't come up for me yet):

 * A depends on B.
 * B depends on third-party library C (so C is not exported by B).
 * When A is compiling (and includes exported source of B), it may fail if A
   does not also depend on C (because C won't be included).