Added CHDK support

Added so M240 can be used to trigger CHDK instead of sending an IR signal, see more about CHDK here http://captain-slow.dk/2014/03/09/3d-printing-timelapses/
Added CHDK support

Added CHDK support to take pictures instead of doing an IR command, see more about how to use it here http://captain-slow.dk/2014/03/09/3d-printing-timelapses/
Add support for disabling encoder control for feedrate multiplier

Signed-off-by: Matthew Schick <matthew.schick@gmail.com>
Merge pull request #829 from blddk/Marlin_v1

Added CHDK support
Merge pull request #833 from mattsch/optional_feedrate_multiplier

Add support for disabling encoder control for feedrate multiplier
Merge branch 'Marlin_v1' into Marlin_v1_Mendel90_personal