rename app 'klp' to 'schools', refs #16
remove Assembly model, it was an unneeded model from previous db tables
refactor models into separate files in models/ folder, as per #13
add m2m relation between Student -> Class and Teacher -> Class through StudentClass and TeacherClass
Merge branch 'refactor_models' into develop
import base models from common.models
rename base -> choices now that the only thing left there is choices definitions