Update version 3.31.1

Update version 3.31

Merge branch 'dev'

# Conflicts:
#	assets/css/public.css

 + v.3.4 l10n added.

 + v.3.4 release.

Leyka 3.2 released

 * L10n updated for 3.0.4.

 + v2.3.6.1 release info added.

 * PayPal checkout.js integration - possible bugfix reference added.

 * Fix for new stable version in readme.

* Fix for core active recurring method without access to the Leyka in…

…stance.