Previously only the top level help message would ever be displayed,
this was caused by 'parse_known_commands' automatically displaying the
default help message and exiting before any of the custom plugins are
loaded. Now ensure this flag is never passed into the method.
In order to properly enable verbose logging for plugin enumeration,
verbosity option must be extracted before commands are processed, and
therefore before all valid arguments are known.
ArgumentParser.parse_known_args() is used for this, which will collect
all unexpected arguments into an "extras" list, rather than raising an
error. This, however, has an outstanding bug, where if say option '-v'
is known and '-f is unknown, args '-v -f' will be parsed correctly (with
'-f' being collected into extras), but '-vf' will not, resulting in an
error.
To get around this, pre-process sys.argv to detect joined options and
manually split them into separate args.
Changing the way target descriptions work from a static mapping to
something that is dynamically generated and is extensible via plugins.
Also moving core target implementation stuff under "framework".