Add tests for upcoming skip and limit functionality

Note: The reason why it should be supported to do skipping and limiting
simultaneously using only one of the functions is to avoid unnecessary
updates (e.g. in paginate scenarios, each function will trigger an
update of the reflist which is unnecessary - only one update needs to be
called once both has been set)
Implement skip and limit functionality
Merge remote-tracking branch 'origin/filter-skip-limit' into updated

Conflicts:
	lib/Model/filter.js
	test/Model/filter.mocha.js