Gphoto2

1/ Fixed failure to build with Python 3.
2/ Made gp_camera_trigger_capture thread aware.

1/ Bug fix: would not build with some versions of SWIG.

1/ gp_file_get_data_and_size() now returns a Python bytes object.
2/ gp_camera_wait_for_event() now returns data for some events.
3/ gp_camera_file_get() now allocates the returned CameraFile.

1/ Improved "docstring" documentation of each function.
2/ Slow operations no longer block other Python threads.
3/ Improved build process.

1/ Added "member functions" to many gphoto2 types to replace the higher level
classes defined in Python.
2/ Removed the "higher level classes" defined in Python.
3/ Added __len__ and __getitem__ members to list-like gphoto2 types.
4/ Improved error handling.
5/ Improved memory safety.

1/ Many more functions now allocate and return their outputs, instead of
requiring a new object as a parameter.
2/ Several of the list-like GPhoto2 types can now be iterated over in Python.
3/ Improved memory safety.