ENH: add 'subcommand' handling to wmake (#1693)

- initial split of wmake-related commands into "plumbing" and
  "porcelain" akin to how git handles things.

- wmakeBuildInfo (very low-level), now relocated to the wmake/scripts
  and accessible for the user as "wmake -build-info".

  This satisfies a long-standing desire to access build information
  in a fashion similar to the api/patch information.

CONFIG: avoid git information when building with a debian/ directory

- when a 'debian/' directory exists, there is a high probability that
  the '.git/' directory is from debian and not from OpenFOAM (ie,
  useless here). This corresponds to an implicit '-no-git', which has
  no effect when building from pristine sources.

ENH: wmakeCheckPwd becomes scripts/wmake-check-dir

- accessible for the user as "wmake -check-dir" and with 1 or 2
  directory names. A wmakeCheckPwd symlink left for compatibility.