Rescale the waterfall pixmap when the GUI is resized

Previously the waterfall would be blacked out when the GUI was resized.
Add Qt 5 support.
Only include Qt widgets if we are using Qt 5.
Merge pull request #76 from weinholt/master

Rescale the waterfall when resizing
Updated.
Updated readme.
Fix mouse input with latest Qt 4.8
Add HackRF Jawbreaker to æist of supported devices.
Add HackRF sample rates.
port to gnuradio 3.7 API
Add usable version string for release builds.
Recommend gnuradio 3.6.5.1 when using gr-audio.
Make output device selector editable with when using gr-audio.

Related to issue #50.
Always reset audio output device on Mac OS X.

This hopefully fixes issue #66 and issue #78.
Add define for identifying OSX in non-Qt code.
Updated news file.
Ensure that FFT window is reset when FFT size changes.

Closes issue #70.
Updated readme.
Merge pull request #80 from pinkavaj/gnuradio_3.7_02

Switch to gnuradio 3.7 API (use gr3.6 branch for legacy).
Include gnuradio-fft as dependency.