EdX testing notes

[achirkin]

• customize submission message in self-paced runs
• Hide download geometry button for edX students
• redundant "You are now logged in" message after design is submitted by edX student
• make lines visible
• update FAQ section
• If user is not logged in and views a student submission, the user can move blocks. He should not be able to do that
• Hide "Compare designs" card for non-logged-in users.
• Change "Use geometry editor" for non-logged-in users to demo page containing one example scenario in full editing mode