Fix escaping of asterisks in AQL documentation.

Asterisks need to be escaped with backslashes, but if surrounded by square brackets, the brackets need to be escaped as well. Does not apply to parentheses it seems, but maybe other characters with special markdown meaning.
Merge branch 'devel' of https://github.com/CoDEmanX/ArangoDB into CoDEmanX-devel

Conflicts:
	Documentation/Books/Users/Aql/Advanced.mdpp
	Documentation/Books/Users/Aql/Functions.mdpp
	Documentation/Books/Users/Aql/GraphOperations.mdpp
	Documentation/Books/Users/AqlExamples/Grouping.mdpp
Merge branch 'CoDEmanX-devel' into devel