Added automatic end-stop offset calbration to M206:

M206 P X Y Z
When P is available in the line, every named axis will be assumed to be zero,
and the calculated offset inserted into memory.
Repairs issues surrounding homing for scara systems
Scara systems are not deltas, and just specifying delta homing will cause
issues in other mudules, such as zprobe
Merge pull request #525 from RepRapMorgan/scara_updates

Repairs issues surrounding homing for scara systems
Merge pull request #524 from RepRapMorgan/M206_improvements

Added automatic end-stop offset calbration to M206:
Move M206 improvements to M306 and leave M206 as is
Merge pull request #527 from wolfmanjm/feature/modify-new_m206-changes

Move M206 improvements to M306 and leave M206 as is
add an additional offset to M306 if Z has a value other than 0
Merge pull request #528 from wolfmanjm/upstreamedge

add an additional offset to M306 if Z has a value other than 0
fix M306 as per qharley (with improvements)
Merge pull request #529 from wolfmanjm/upstreamedge

fix M306 as per qharley (with improvements)
add md5sum for bootloader hex
Merge branch 'edge' of github.com:Smoothieware/Smoothieware into edge
allocate secind serial to AHBO
disable DFU by default
add dfu_enable to config
Merge pull request #530 from wolfmanjm/feature/disable-dfu-option

Feature/disable dfu option
update firmware.bin with dfu disabled
add DISABLEMSD to options allowed on make command line
Merge pull request #531 from wolfmanjm/upstreamedge

add DISABLEMSD to options allowed on make command line
add a disablemsd version of firmware.bin
fix ls