LimeSDR support fixes
- Try to fix lockup situation when Rx and Tx run concurrently and changes are made on one side while the other is running. Handle suspend / resume streams correctly and when appropriate. Handle calibration when appropriate. Added a 0.1s delay after starting and stopping a stream. This should fix issue #83
- Handle ADC or DAC sample rate change correctly thus allowing possible different host/device sample rates between Rx and Tx. This fixes issue #82
Non functional changes
- split sdrbase library into sdrbase and sdrgui. The sdrgui library will contain the common GUI part that depends on QWidget and OpenGL and sdrbase will not be dependent on GUI libraries and therefore compatible with a console application (future SDRangel server).