fixed simple eval view and modified rubrics edit

Simple eval view uses the same element as the actual simple
evaluation form the student fills out including the instructions
at the top. The instruction that was added earlier which tells
the students when the evaluation stops being accessible caused
a bug because the preview does not have a date to display. I've
fixed it by replace the date with a string that says Evaluation's
release end date.

I've also removed the button linked to the edit view for rubrics
to keep it consistent with the other evaluations. Simple and mix
evaluations and surveys view do not have links to the edit page.
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modified groups import

When I've tried to import 3000 students into a group, the process
took more than 60seconds which made the application crash. I rewrote
the function to import groups to make it more efficient.
modified the groups import and groups import result view

I have modified groups import to not include group number as
a valid field. It now only says the group number is auto
generated.

I have also modified groups import results to display possible
reasons for the failures.