Closes #191: Remove index in annotation_categories

- Remove of last migration
Closes #1120: Grader should go to submissions

 - add of the rule for the grader to see the sub_menu in submissions
and results pages.
 - modification of tests which were, for me, obsolete.
Closes #1105: Be able to download all files with annotations

 - addition of the action 'download_zip' in ResultController
 - modification of the style to do not add a 'return' in the form
 - addition of the button 'Download all files' linked with the
'annotation' checkbox
addition of a message
Closes #265: Adding possibility to map grader to section

 - addition of a select in graders/index
 - modification of the filters tables, addition of a rule
Fix bug UI in browse

In reference with (PR) #1116 wich leave a bug in the display.
Closes #1124: Problems with importations

 - modification of the mistake
added tests
Closes #197: Encoding breaks

In reference with #197.

- added a Iconv encoding to allow possibility unlock codeviewer.
Merge pull request #1121 from GhiGt/issue-191

Closes #191: Remove index in annotation_categories
Merge pull request #1129 from GhiGt/bug-ui

Fix bug UI in browse
Merge pull request #1123 from GhiGt/issue-1105

Closes #1105: Be able to download all files with annotations
Merge pull request #1130 from GhiGt/issue-1124

Closes #1124: Problems with importations
added i18n for section
Merge pull request #1131 from GhiGt/issue-197

Closes #197: Encoding breaks with non utf-8 files
added ':' to section's name
Closes #1133: Security flaw in download action

- edited authorized_to_download? method in ResultController
Merge pull request #1137 from GhiGt/issue-1133

Closes #1133: Security flaw in download action
Merge pull request #1128 from GhiGt/issue-265

Closes #265: adding possibility to map grader to section
Merge pull request #1122 from GhiGt/issue-1120

Closes #1120: grader should go to submissions