xcsoar: Replace manually built XCSoar tools by new xcsoar python package
tests: Removed xcsoar tools mocking

This is no longer needed since we can easily install and use the xcsoar
tools now.
xcsoar: Renamed lib.xcsoar to lib.xcsoar_ to avoid name conflict

Importing xcsoar in lib.xcsoar caused some problems when running nosetests
Merge pull request #154 from Turbo87/xcsoar-tools

Replaced manually built XCSoar tools by new xcsoar python package