Added epub export function
Fixed a bug into PHPePub with special caracters
Big changes for epub export. Now possible to do it from a tag, a category and a search. Also, improved ebook rendering.
Changed template organisation
Many improvements to epub produced : better cover, better tags
Added translation capabilities for epub system
Updated the french translation
Merge pull request #680 from m-r-r/fr-1.6.1

French translation update
Merge branch 'dev' of https://github.com/wallabag/wallabag into epub
Fix bugs and improved epub rendering
Better names for epub files and epub in all themes now
Merge branch 'epub' into dev

Conflicts:
	themes/baggy/home.twig
Cleaned epub fonction