Add PostBuildEvent to all pvr addon projects that robocopies their output to the local xbmc addons directory, when the project is part of the "XBMC for Windows" solution

Update README file to indicate the pvr projects have the PostBuild action included
Rename libcmyth project (project filename,  projectname and GUID only, not the name of the built library file or namespaces etc) to avoid it clashing with libcmyth_dll in the XBMC solution

On the XBMC side libcmyth was renamed to libcmyth_dll in the past but the actual vcxproj name is still libcmyth.vcxproj which was causing a duplicate project when adding pcvr projects into XBMC solution)