Added Xcode project for OpenEphysHDF5Lib, which builds a shared library (libOpenEphysHDF5.dylib) and installs it in open-ephys.app/Contents/Frameworks.  On macOS, the KWIKFormat plugin now links against libOpenEphysHDF5.dylib.

Added Xcode config files for building dylib's that are embedded in open-ephys.app/Contents/Frameworks

* Now when we compile plugins it checks whether plugin's folder
  contains *.jucer file and appropriate Makefile for plugin in the
  Source/ folder.

* Fixed OpenEphysLib files;
* RHD2000Thread class some refactoring and stylystic fixes.

addresses #74