Add a disk printer

Description

Add a disk printer for debugging purposes.

Basic usage

com::ContextItem::print_tree(root_folder);

Possible output

Welcome to the ==INCREDIBLE DISK PRINTER== by xbabic :)
maker/
├── camera/
│   └── frame
├── grid/
│   └── frame
├── updater.run
├── presenter.run
└── test_box/
    └── frame

Signed-off-by: Petr Babic xbabic@fi.muni.cz