BuildPropertiesParser should use reactor project instead of basedir do the work

[laeubi]

BuildPropertiesParser uses a rather strange approach of taking a basedir and then using the basedir to find the maven project via the maven session.
The callers of BuildPropertiesParser already have a project and call basedir on the project...

Beside this, this requires the LegacySupport component to obtain the session of the current thread what makes it problematic if code runs in background threads or if we ant to make Tycho a core extension see #556

The proposal is to simply pass the project around instead of the basedir.