[QT] thumbnail polish + log colors

[Megamouse]

@AniLeo in case you want to change the color in your stylesheet let me know and I'll append it

Example use in stylesheet:

QLabel#thumbnail_icon_color { color: rgba(100, 100, 100, 255); }

QTextEdit#tty_frame { background-color: #ffffff; }
QTextEdit#log_frame { background-color: #ffffff; }
QLabel#log_level_always { color: #107896; }
QLabel#log_level_fatal { color: #ff00ff; }
QLabel#log_level_error { color: #C02F1D; }
QLabel#log_level_todo { color: #ff6000; }
QLabel#log_level_success { color: #8000; }
QLabel#log_level_warning { color: #BA8745; }
QLabel#log_level_notice { color: #000000; }
QLabel#log_level_trace { color: #808080; }
QLabel#log_stack { color: #000000; }

I also made the default stylesheet code a bit more readable