mysql2postgres massive changes
remove only _empty_ virtual lessons
remove unprintable chars from descriptions
next move to postgres
correct invalid UTF-8 stuff
mini_test
2postgres
do not require all virtual lessons to be filmed on the same day
2postgres
Merge remote-tracking branch 'origin/master' into mysql2postgres

Conflicts:
	Gemfile
	Gemfile.lock
	app/models/container.rb
	app/models/lesson_description.rb
Merge branch 'mysql2postgres'