MultiAccountContainerSpecial troch someusefulladdons

Rework of original FF addon Multi Account Containers.
I corrected all incomplete languages, added selfrenaming of containers and colored icons in URL line and TAB title for better visibility. As far as my work is concerned i can guaranty, that this addon will not send any data to any third party, it will only do what it is meant for and has no hidden whatsoever purpose. I like this addon because i finally can work with multiple webmail accounts parallel.