Fix #28: Add support for b3aggrcon and b3aggr files

With this commit it gets possible to includes b3aggr files
directly in a target platform definition.
This allow to express things like :
"I rely on what the amalgam project contributes to Luna"
by using :

include
"http://git.eclipse.org/c/simrel/org.eclipse.simrel.build.git/plain/amalgam.b3aggrcon"

or :
"I want the cdo version contributed for Kepler SR1"
with :
include
"http://git.eclipse.org/c/simrel/org.eclipse.simrel.build.git/plain/emf-cdo.b3aggrcon?id=KeplerSR1"

The b3aggrcon resource content is parsed on the fly
to produces instances of TargetPlatformDSL.

Known limitations :
- only the "repositories" and their children are used
( no platform filters..)
- only features and bundles are used
(no category mapping or exclusion list.)
- references within a b3aggr file are not resolved.

https://git.eclipse.org/c/simrel/org.eclipse.simrel.build.git/plain/simrel.b3aggr

Gives you nothing as all the actual contributions are in the included
*b3aggrcon files.
Stack is more than deprecated. Pleas use up to date java API (e.g. Deque). The project already only works on Java 6, no need to stick with previous APIs.