ENH: makeParaView now accepts paraview-VERSION directly as argument

- Symmetrical with the usage for most other ThirdParty build
  scripts. For example,

      "makeParaView ParaView-5.0.1"

- As a convenience, also allow a number directly. For example,

      "makeParaView 5.0.1"

  This should be clearer than the old instruction and does not
  rely on an alias:

      "foamPV 5.0.1; ./makeParaView"

BUG: heuristics for activating GL2 rendering backend missed when
     paraview version was specified from the command-line