Merge pull request #102 from bgamari/fixes

Player: Reduce block queue depth to 16
Gcode: Ensure queued is initialized

This was a silly and obvious oversight from
6a3328dfe514e66a98c0cf5adc7252d333567e83. Thanks to wolfmanjm for
spotting it.
Merge pull request #104 from bgamari/edge

Gcode: Ensure queued is initialized
CircBuffer: move USBSerial buffers into USB ram to conserve main ram
CircBuffer: use actual size specified, report free space correctly
USBSerial: enough room in buffer for 2 full USB packets, plus a little extra to maintain alignment
USBSerial: call USBHW::usbisr() to drain queue when necessary
SimpleShell: cat: use puts instead of printf("%s") for efficiency
USBSerial: remove redundant commented code
Merge branch 'feature/USBSerial-works-outside-ISR-context' into edge
added new simplshell commands progress, abort and help
Merge pull request #105 from wolfmanjm/feature/playprogress

added new simpleshell commands progress, abort and help
rebuilt rostock solution into modern edge
change switch to if/then/else for solution selection, so it compiles under DEBUG
Merge pull request #1 from wolfmanjm/fix/solution-selection

change switch to if/then/else for solution selection, so it compiles und...
commented the second usbserial to simplify life for new users
Merge pull request #108 from logxen/edge

commented the second usbserial to simplify life for new users
Merge branch 'edge' into rostock2
Added position reset at homing end; Added min and max axis positions.
Accidentally left a hard-coded position in.