LanguageLoader: Location of language files should be dependent on the assembly

[Lakritzator]

Currently all file locations need to be passed when initiating the loader, this should be partly dynamic.
When an ILanguage is added, the framework should check for files relative to the assembly location.
This would make it easier to use extensions, it should be clear (maybe via an attribute) where the files are located.

[Lakritzator]

Also the usage of Assembly.GetManifestResourceNames & Assembly.GetManifestResourceStream should be added, this helps when resources are inside the dll.