PS_ON configurable boot state

Allows the user to select wheter or not the PSU should be turned on or
kept in standby when marlin boots
Merge pull request #630 from dumle29/Marlin_v1

PS_ON configurable boot state
Made instructions more clear.

Not sure what happened to my last commit so this includes that one + reordering the steps.
Merge pull request #632 from dbenamy/Marlin_v1

Made instructions more clear.
Fix servo control for Melzi
Add (correct) missing pin definitions for Y2

I tested this and it works.
Add UUID support to M115 responses.
If you have a switch on suicide pin, this is useful if you want to
start another print with suicide feature after a print without
suicide...
Implement M226 - GCode Initiated Pause

Implemented M226 as described here:
http://reprap.org/wiki/G-code#M226:_Gcode_Initiated_Pause

Waits for pin to be become either HIGH, LOW or the inverse of what it
was before. Allows printing to pause until user interaction
Merge pull request #635 from dbenamy/Marlin_v1

Add (correct) missing pin definitions for Y2
Merge pull request #636 from PrintToPeer/Marlin_v1

Add UUID support to M115 responses.
Merge pull request #637 from justuswilhelm/Marlin_v1

Fix servo control for Melzi v2.0
Merge pull request #640 from fmalpartida/SAV-MkI

Added support for BT on AT90USB devices, corrected LCD bug, added new board and LCD
Merge pull request #641 from hugokernel/master

M80 - ATX Power On related modification
Merge pull request #647 from shaggythesheep/newfeature-M226

Implement M226 - GCode Initiated Pause
Fixed compile errors from bad commits.
Merge remote-tracking branch 'origin/Marlin_v1' into SAV-MkI