Feature: Maps and Multi-Maps should support appending a single map rather than just...

Feature: Maps and Multi-Maps should support appending a single map rather than just an entire set.

This is really an oversight on my part.
The append should by default append a single item.
To append an entire set, a new function should be used (an append all function).

This should be done for all of the string types that are applicable.
Such changes are left for the next release and are not planed for the 0.5.8 release.

This functionality is necessary for bug fixes in the controller program.