Some restructuring.

All geometry manager methods that apply to a master widget instead of
to a slave widget have been moved to the Misc class, which is
inherited by all of Tk(), Toplevel() and Widget().  They have been
renamed to have their geometry manager name as a prefix,
e.g. pack_propagate(); the short names can still be used where
ambiguities are resolved so that pack has priority over place has
priority over grid (since this was the old rule).

Also, the method definitions in the Pack, Place and Grid classes now
all have their respective geometry manager name as a prefix
(e.g. pack_configure); the shorter names are aliases defined through
assignment.

A similar renaming has been done for all config() methods found
elsewhere; these have been renamed to configure() with config being
the alias (instead of the other way around).  (This may not make much
of a difference but the official Tk command name is now 'configure'
and it may help in debugging tracebacks.)

Finally, a new base class BaseWidget has been introduced, which
implements the methods common between Widget and Toplevel (the
difference between those two classes is that Toplevel has a different
__init__() but also that Toplevel doesn't inherit from Pack, Place or
Grid.