[QAE1037] Admin: read_only view of form

Review 'read only' version of the form

```
As a Admin 
I want to be able to see the forms (read only) but exactly as the user filling it in would see it
So that I can have 'read only' version of form
```

So, basicly implemented:
* ability for Admin to login in as user (via device's standart login bypass feature)
* Added standart 'disabled' attribute and 'read_only' css class for most html controls on form (input,s textarea, radio etc)
* Resticted access for admin to update/ create/ destroy actions in controller level
* Added basic Rspec test for it
yeah, I got strange error:
that @questions are nil