Changing the order of the QGCFileDialog::getSaveFileName() function. The idea was to expand the existing QFileDialog version but as we removed the selectedFilter, we might as well make this more intuitive. The options argument is the one trully optional and should be last.
Adding an example to the documentation on how to go about figuring out what file type was returned by these functions.

Removed the “selectedFilter” argument from the QGCFileDialog functions along with references to it in unit tests.
Fixed function declarations and prototypes formatting while at it.
Changed the caption of a few file save dialogs with a more descriptive text (explicitly telling what is being saved).

Tweaking the documentation for QFileDialog and replacing the doxygen "@" escape to be consistent with the rest of the code.

WIP issue #1173. Adding default suffix (extension). While at it, added selected filter support and removed unit test assert about its use.

Using QFileDialog directly on OS X can hang intermittently due to Qt
bug. QGCFileDialog works around this by not using the native dialogs.