Engine cleanup.
Removed dead/unused functions from engine.
Further engine cleanup.
Moved string trimming functions to seperate utils module.
Engine code cleanup:

- Put functions in sensible order in file.
- Added missing prototypes
- Removed unneeded headers
- General cleanup.
No more passing of global config.
Different handling of global playlist, mp3list and config.
Removed dead functions and initial cleanup in controller.
We write c11 code, more controller cleanup.
Controller cleanup.
Unused defines.
Removed accidental add, added to gitignore.
Config cleanup.
Songdata header cleanup pt1.
Songdata header cleanup pt.2

- Merged song.c with songdata.c
- Moved dirstack functions to own header
gui cleanup.
Move of http controller to plugins dir, not working yet, macro fubar.
added http controller
Plugin dir restructuring
Restructured plugin folder.

Removed plugin support and deps, for it is broken.
See issue.