Cmake policy CMP0048 breaks the build by setting the MOOSE_VERSION to NULL

[dilawar]

The lastest cmake (3.6.1 on MacOSX) sets the PROJECT_NAME_VERSION by itself to NULL when not set in project macro i.e. MOOSE_VERSION is set to NULL by default.

This variable is used by CMake to pass the version information to C++ codebase so that

print moose.__version___

string can be set.