PartPropSvc: patch for bad parsing of input files: GAUDI-1119

In the PartPropSvc, after upgrade to boost::regex, parsing of input
files fails silently if no "=" is present in the token (ie file type
is not specified), and the file loaded will be the default table
instead of the user supplied one.

eg: InputFile = "myPDGTABLE.MeV" will result in "PDGTABLE.MeV" being
loaded instead, with no message that this has taken place.

Fixes GAUDI-1119.

See merge request !59