create qmake2qbs tool

we need a tool to semi-automate migration from qmake to qbs.

the tool should be intelligent enough to:

• map pro and pri files to Modules, also nested ones (see QBS-573)
• collect sources, including VPATH
• collect dependency declarations via QT
• recognize and map simple conditions. to do that, the project evaluator will need to tag values with the condition stack each assignment is in.
• possibly recognize a bunch of qt module specific constructs to ease the migration of qt itself.

ideally, the original .pro file should be pasted into the .qbs file as a comment, annotating what has been migrated and what needs manual treatment. however, that may be a bit hard to accomplish if the migrator works on the evaluation result, not the sources.