Make a few changes:

1. Add color support to OglDrawable, used by ParameterizedSurface so far

2. What to do if exit called from Python interpreter? no idea yet

3. Check for drawable under the mouse during OglViewingArea::mouseDrag
Fix the bug in shader window ownership - clear nullptr's first
Try to write a thread-safe shader compilation step
Merge branch 'Python' into Linux
Fix seg-faults with the Boy's surface and file browser on Linux

1. Something in std::complex was causing the seg faults

2. Python is still disabled

3. The native file browser does not work on Linux, using JUCE's