Added XB-200 transverter support

Native methods added along with GUI modification
Totally untested yet!
Add precompiled version of libbladerf

In order to ease the installation for windows users that don't
want to install Visual Studio and all dependencies, I added
precompiled version of bladeRF libs and tools.
Fixes a race condition + bad XB-200 handling

There was a race condition preventing the thread to be sampling.
In addition to that, XB-200 filter functions were called even
though the module was not enabled.
Remove unnecessary dll

SDRSharp.Common.dll and SDRSharp.Radio.dll are only required to
compile source code.
As they may not be kept up-to-date, they are removed from the
repository.
Create README.md
Attempt to fix the display issue of README.md
Fix potential crash

During some error cases, the GUI component raise an exception that
led to a crash because the code was trying to call Dispose() on
null pointer.
Forgot to update Debug precompiled version
Updated README.md
Updated libbladerf
Merge branch 'master' of github.com:jmichelp/sdrsharp-bladerf