French translation: cleanup

Report modifications in english language file (en.php)
5ee5de1
Fixes some typos and general consistency
Small fixes for consistency
Clarifies strings for uploads
Changes installation headline for consistency
Updated credit for translation

Rendons à César…
bugfixes and smarter options for selectboxes, checkboxes and radio
Better translation for "structure" fields
Fix #138
Fix #139
Fix #133
Fix #127
Merge pull request #115 from bugsysop/french

French translation: cleanup
Fix #142
Fix #141
less fontawesome files and new local source sans pro version
Fix #137
Fix #136
Fix  #52
Fix #159