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".
