Add class_and_number field to student, clean specs
Some fixes
Totally WIP
Merge branch 'counter_cache' of https://github.com/kalkov/GAKUEngine into counter_cache

Conflicts:
	core/spec/requests/admin/disposals/student_addresses_spec.rb
Patch AR because of counter_cache double increment issue
Merge branch 'counter_cache' of https://github.com/kalkov/GAKUEngine into counter_cache
[fixes] counters