Merge pull request #282 from wolfmanjm/upstreamedge

make play quiet by default added -v for verbose
Remove errant object files that should never have been in the source tree in the first place
incomplete implementation of multi-extruder support. backwards compatible
MBED::Serial: improved baudrate calculator. see http://github.com/mbedmicro/mbed/pull/116
Add M400 which waits for all moves to complete before returning ok