XML lib: More kw docs.
XML lib: More kw docs.

Update issue 1234
Documented Copy Element and Save XML.

Now all new keywords have docs and they are ready for review. The
latest generated version of the documenation is available at
http://robotframework.googlecode.com/hg/doc/libraries/XML.html

fiuba08/robotframework,ldtri0209/robotframework,ldtri0209/robotframework,fiuba08/robotframework,waldenner/robotframework,fiuba08/robotframework,ldtri0209/robotframework,waldenner/robotframework,waldenner/robotframework,fiuba08/robotframework,waldenner/robotframework,waldenner/robotframework,ldtri0209/robotframework,fiuba08/robotframework,ldtri0209/robotframework