Sort/prettify imports with isort
[GTKUI] All files Flake8'd and use new header
[GTKUI] Fix isort error in gtkui
Flake8 core and common files

 * Added N802 to flake8 ignore as certain inherited funcs cannot be changed
   to lowercase and this unresolved warning hides other errors/warnings.
 * Include new header
Remove unneeded ez_setup and 'isort' imports
[WebUI] Fix isort error in auth
[WebUI] Small fixes to text labels