v0.6.8

• Rework native library
• Return fmi2Discard, not fmi2Error from unsupported fmi2GetXXStatus
• Implement fmi2GetBooleanStatus (needed by som importers when step returns False (fmi2Discard).
• Fix classvars not being picked up in modelDescription.xml
• Removed (native) sources from FMU.

Changes should be backwards compatible.