MDTextField: Add color_mode
Adds color_mode property to MDTextField:
This property controls the color of the textfield when it is focused.
- When it is set to 'primary', it will use primary color (like old behavior)
- When it is set to 'accent' it will use accent color
- When it is set to 'custom' it will use whatever color is put into the 'line_color_focus' property
This MR also cleans up some silly old code from MDTextField, that actually didn't do anything anymore.
@ngoonee can you test out? There is a demo in KitchenSink