Rewrote lots of the code

Rewrote a fair bit of code. WARNING: Redesigned the GUI in QtDesigner to follow the native Qt standards (does not use the PNGs). 

Submiting the .ui file as well.

Reconnected the signals.

The program is now using a unified cross-platform main.py file instead of main_linux.py and main_windows.py.

Did not build the binary!