Added learn material class, some random fixes + code style improvements
Added quotations to all identifiers in SQL queries
Added create scripts for the smo SQL databases
Added sqlite database files for the two smo SQL schemata
Added learn_period::get_subject_suggestions()
Added add_lesson action and form
Merge commit '46b2b7fa0d71c875f390d50726755a2ed3df3d36'
Added course::get_course_id(), replace every occurence of SchoolMessOrganizer with SMO
Added subject::get_subject_id, a minor fix
Some work on the timetable
Merge commit '61fdca996e2fb20987be024417cec9db48ae9cac'
Added smo_user::get_learn_period_id
Fixed add_lesson