Merge pull request #495 from mariroz/dev

fix of global $http visibility, issues #493, #494
Merge pull request #499 from mariroz/dev

French translation added by @Draky50110, issue #488
Merge pull request #501 from mariroz/dev

fix of #498, #493, #494 - because disappeared in last commit
Update pl_PL.utf8.po

First cleanup, more to come.
Merge pull request #502 from skibbipl/patch-1

Update pl_PL.utf8.po
translation related: how-to md file added, script to generate php from all twig templates, polish mo file compiled