Multiple versions of same bundle/Bundles and features having same name

Sometimes a tycho reactor may contain multiple versions of a single bundle name (this is the case in eclipse-platform, for example) or a tycho reactor may contain features that have the same symbolic name as plugins (this is the case in eclipse-rse, for example). This is normal and permitted in OSGI, but resulted in either missing or mangled metadata being generated by xmvn-install.

This patchset fixes these cases.