Added the capability to change the language.

I add two files : en.txt and fr.txt for the two languages. The user choose the language in the config.yml file.
Once the plugin is launched, he tried to open this files, if he can't, he extract them from the jar file.
A new variable appear : listStrings who contain all the strings for the selected language.

I don't test this modifs a lot because I haven't the time to install a database.
But as I see, there are no bug at launched.
It's a very little integration, it can be improve a lot !

It's the beginning of a new era :)

PS : BUT I recommend you to test it before doing anything.