Refactor textanswers access control

[jooooosef]

Some users can see textanswers and select some filters for those answers.
The page is results_evaluation_detail.html and gets its content from evaluation_detail.
There are now remove_textanswers_that_the_user_must_not_see and can_textanswer_be_seen_by to control if a user is allowed to see specific textanswers while can_textanswer_be_seen_by also handles the user selected filters. If these filter buttons are not usable then they should be disabled which is handled by code inside evaluation_detail. This leads to code duplication.

This should be changed according to:
#2232 (comment)