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.

README.md

@@ -85,10 +85,10 @@ As can be seen in this example, the git build information is
 supplemented by the date when the last change was authored, which can
 be helpful when the repository contains local changes. If you simply
 wish to know the current API and patch levels directly, the
-`wmakeBuildInfo` script provides the relevant information even
+`wmake -build-info` provides the relevant information even
 when OpenFOAM has not yet been compiled:
 ```
-$ wmakeBuildInfo
+$ wmake -build-info
 make
     api = 1812
     patch = 190531
@@ -207,4 +207,4 @@ ThirdParty directory will contain either an `Allwmake` file or a
 - [Community](http://www.openfoam.com/community/), [Governance](http://www.openfoam.com/governance/)
 - [Contacting OpenCFD](http://www.openfoam.com/contact/)
 
-Copyright 2016-2019 OpenCFD Ltd
+Copyright 2016-2020 OpenCFD Ltd