demos: c_simple: Add pretty print example.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
doc: Update pixels docs.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
doc: Update core docs.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
doc: general: Update BMP implementation state.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>