Implement AndroidServer::Teacher class.

Add all functionality for AndroidServer::teacher class. Also
some bugs were fixed in other classes.
NOTE: AndroidServer::Teacher and AndroidServer::Student classes aren't
testes.
TODO: Test AndroidServer::Teacher and AndroidServer::Student classes,
run all classes on server.
Test Commit

Test commit, ignore it!.
Merge branch 'master' of github.com:bjoerndalen/android_server

Conflicts:
	site_lib/AndroidServer.pm