Add N1QL functions roles

For GA functions we need to be able to add global and scope function related roles.

More specifically we need to be able to grant and revoke

MANAGE_FUNCTIONS (create and drop global functions)
EXECUTE_FUNCTIONS (execute any global function)
EXECUTE_FUNCTION[function] (execute a specific global function)

And those scope specific

MANAGE_FUNCTIONS[scope] (create and drop functions in scope)
EXECUTE_FUNCTIONS[scope] (execute any function in scope)
EXECUTE_FUNCTION[scope:function] (execute a specific function in the given scope)

Could we start with the first set?