Migration to rails 3.1

Done :
 - edited Gemfile
 - moved from public/ to assets/
 - added `config.assets.enable = true` in config/application.rb
 - commented lines about rjs in config/environments/development.rb
 - added lines about uglifier and scss
 - added app/assets/stylesheets/application.css
 - added app/assets/application.js

TODO:
 - move application.js in javascripts
 - resolve images not found
 - remove files not needed like rails.js, jquery.js...
update to rails 3.1.12
resolved sql problem
fix application.js

- moved application.js inside assets/javascripts
- removed jquery.js, prototype.js and rails.js to use the gems.
fix problem with ImageAnnotation
fix deprecation warnings
fix some errors

in
 - annotation_categories_controller_test.rb
 - assignments_controller_test.rb
fix flexible_criteria problems

added some fixtures files
fix some errors in notes_controller and grade_entry_forms_controller
fix some errors in tests

for:
 - results_controller_test
 - rubrics_controller_test
Merge branch 'master' into pr/1153
Merge branch 'master' into pr/1153
mysql2 >= 0.3 required in gemfile as of Rails 3.1
Fix exception type mismatch in create_or_update_from_csv_row in rubric_criterion.rb
Fixed functional test cases for move_criterion
Flash now requires has? rather than has_key?
Fixed issue 728. Uploading an invalid CSV file now shows an error message.
Added error message if encoding of the uploaded file is incorrect. Improved error message and fixed comment typo.
fix issue-1019, added alert warning
Merge pull request #1198 from daniyall/issue-728

Fixed issue 728. Uploading an invalid CSV file now shows an error message