moveconfig: Allow automatic location and adding of 'imply'

By using a Kconfig parser we can find the location of each option in the
Kconfig tree. Using the information from the database we can then
automatically add an 'imply' option into the right place if requested by
the user.

Add a -a option to support adding 'imply' options. Display the location of
any existing 'imply' option so that progress can be examined. Add a -A
option to hide any existing 'imply' options so that already-completed
additions need not be considered further.

Also add documentation for this feature.

Signed-off-by: Simon Glass <sjg@chromium.org>