Filament Changer for Marlin 3D printers GUI

The program now is able to find the layers count in the gcode file (for Simplify3D and Cura) and show a message when the program selected is wrong.

Also, the layer number is displayed to the user in the label, and the maximum layer number to choose in the spinbox is fixed to the number of layers in the gcode file.

I've added the the gui some program selection buttons (and a handler so you can only choose one).

I've also added a icon for the app, that shows on the window and windows taskbar (I haven't runned the program on mac or linux system yet).

Also, I've added a function that makes the program appears at the center of the screen.

Conected slots and signals, created functions for save, browse and export buttons. Also, created the first script to look for the keyword layer in the file.

Created the first sketch of the gui itself and the python controller