Fixes several files incorrectly stated a different license from the actual project, as well as the copyright headers included in all files. This change has no effect on the licensing terms, it should clear up a bit of confusion by contributors. Plus the files get a bit smaller, and we have less duplicated information across the entire project.
Overall the project is GPLv2 if not built with Qt, and GPLv3 if it is built with Qt. There are no parts licensed under a different license, all have been adapted from other compatible licenses into GPLv2 or GPLv3.
While the long descriptions were useful, keeping the updated and translated is pretty much impossible. Technology moves fast and not everyone that translates the project knows a lot about technology.
Therefore the long descriptions have now been replaced with a button that opens the wiki page for the feature instead. This should drastically reduce the number of help cases, and improve the translation coverage at the same time.
This header includes all common data between headers used in the plugin. This should improve cross-platform compiling support whenever possible, as all platform-dependent common includes and defines can be done here.
