Closes #969: Removed fake path in message
Closes #1111: Possibility to download all submissions from all groupings

 - added link to download
 - added action download_groupings_files in SubmissionsController
bug fixed
Closes #1136: Switching revision number

 - added a revisions_history attribute to repo_browser
 - added a select in repo_browser
fix i18n
Closes #1126: Missing fields in an Assignment

 - added validates to :description and assignment_stat
removed old form tag
added functional test
Merge master
Merge branch 'master' of github.com:benjaminvialle/Markus into issue-1126
Merge branch 'master' into issue-1126
Merge branch 'issue-1126' of https://github.com/GhiGt/Markus into issue-1126
Merge pull request #1132 from GhiGt/issue-969

Closes #969: remove fake path in message
Merge pull request #1134 from GhiGt/issue-1111

Closes #1111: possibility to download all submissions from all groupings
Merge pull request #1142 from GhiGt/issue-1136

Closes #1136: Switching revision number