Parametrized miter box with two versions of channel labeling that can be turned off.

Attached .stl files are with following parameters: ``` box_width = 40; box_length = 100; box_height = 30;

box_floor_heigth = 5; box_wall_width = 5;

channels = [30, 45, 90]; channel_width = 1.5;

add_channels_description = true; text_height = 4; ```