ENH: isolate version information in foamVersion names instead of globals

- For compatibility, access to the old global names is provided via
  macros
        #define FOAMversion     foamVersion::version
        #define FOAMbuild       foamVersion::build
        #define FOAMbuildArch   foamVersion::buildArch

- this isolation makes it easier to provide additional scoped methods
  for dealing with version related information.  Eg, printBuildInfo()