[code-reflection] Integrated: Hat bld and dir changes in prep for separating native ffi and jextracted backends

[Gary Frost]

This looks like a huge change, but is mostly moving backend files around to allow us to have ffi backends (needing cmake to compile c++ source), jextracted backends (which rely on jextract to allow us to skip cmake) and pure java backends (sq and mt)

So under backends we now have an extra dir

backends
    +-- ffi
    |         +-- opencl
    |         +-- cuda         
    +-- jextracted
    |         +-- TBA
    +--java
    |       +-- seq
    |      +-- mt

The various project java srcs also have the appropriate packege name (say hat.backends.ffi.opencl) to avoid collisions if we were to ever consider including both in the path. 
 
This does effect how we run examples.  We need to include the 'type' of backend with hatrun, so 'ffi-opencl' instead of previous 'opencl'

java @ bldr/hatrun ffi-opencl heal

-------------

Commit messages:
 - whitespacery
 - updated docs and sanity script
 - Started work on jextracted opencl backend.  Cleaned up CLWrap.
 - prep for creating jextracted opencl backend
 - sync scripts with upstream
 - Swapped native for ffi so we can use package name
 - maven pomery
 - Some minor bld changes to reflect backend separation (java/native/jextracted)
 - Exposed java-mt and java-seq iml files
 - Moved 'native' backends to backends/native
 - ... and 2 more: https://git.openjdk.org/babylon/compare/2d6b5763...ae3e4ae2

Changes: https://git.openjdk.org/babylon/pull/297/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=297&range=00
  Stats: 8413 lines in 168 files changed: 4572 ins; 3139 del; 702 mod
  Patch: https://git.openjdk.org/babylon/pull/297.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/297/head:pull/297

PR: https://git.openjdk.org/babylon/pull/297