more consistent naming convention for aliases

- old-style (left untouched for now):
  app, lib, run, sol, tut, util

- new-style:
  foamApps, foamLib, foamRun, foamSol, foamTut, foamUtils

- additional aliases:
  userApps, whichFoam

NB: ideally we'd have 'foamSrc' instead of 'src'.
    Do we really need 'foamsrc' and 'foamfv' anyhow?