We have agreed to develop a meta-tool named "west", which will be a
swiss-army knife of Zephyr development. It will support use cases like
building, flashing and debugging; bootloader integration; emulator
support; and integration with multiple git repositories.

The basic usage for the tool is similar to git(1):

    west [common opts] <command-name> [command opts] [<command args>]

There are common options, such as verbosity control, followed by a
mandatory sub-command. The sub-command then takes its own options and
arguments.

This patch adds the basic framework for this tool, as follows:

- a Python 3 package named 'west', in scripts/meta. There is no PyPI
  integration for now; the tool will be improving quickly, so we need
  to keep users up to date by having it in tree.
- an main entry point, main.py, and a package-level shim, __main__.py
- a cmd subpackage, which defines the abstract base class for commands
- logging (log.py)
- catch-all utilities (util.py)
- Windows and Unix launchers so users can type "west" to run the tool
  after sourcing the appropriate zephyr-env script for their
  environment.

Subsequent patches will start to add individual commands.

Signed-off-by: Marti Bolivar <[email protected]>