Moved some controls on the GUI

Samplerate and bandwidth are now on the same row
Gains have been reordered (LNA -> VGA1 -> VGA2)
Fix lower samplerates usage

- Reduce timeout from 3s to 1s
- Buffer size is now dynamically changed according to the selected
samplerate
- Moved bladerf_sync_config() call in the thread to ensure thread safety
- Add a lock on _readLength for thread safety
Fix a potential crash

SDRSharp was crashing when hitting the stop button if the device has
been lost while sampling. This was due to a loop of exception.
Merge branch 'master' of https://github.com/jmichelp/sdrsharp-bladerf