XML lib: Documented new keywords.
XML lib: Documented new keywords.

Update issue 1234
Documented the following keywords:
Set Element Tag
Set Element Text
Set Element Attribute
Remove Element Attribute
Remove Element Attributes

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