Use Language strings in Frontend (messages and layouts)

[piotr-cz]

Use language strings in extensions to allow translations front-end side (\helper.php and \tmpl\**)

[abemedia]

As far as I can see all the messages in helper.php already use language strings. Will update the files in \tmpl\ though.

[piotr-cz]

True, I must have mixed something up

[abemedia]

I just realised the forms that come with the module in /forms/ don't use language strings though. Will sort it out at some point over the next few days.