Fix Menu issues

Fix menu navigation issues:
Better control of position in menu
Add check to not to be over the limit of 4 level of menu/pages
Add a way to disable auto return menu instead of periodical reset for
long duration command
Make navigation consistent :
If no issue return to menu position
If any issue/cancelation return to main screen to see status
Correct isHomed function to check X,Y,Z home

Correct isHomed function to check X,Y,Z home, as today even if only is
homed - function return true, so add a flag for the X home, Y home and Z
home and check all 3 to set is homed or not, each home can also be
checked separatly
Add manual leveling, update Load/Unload function

Add manual bed leveling, update Load/Unload function with menu position
control
Merge pull request #16 from luc-github/davinci

Merge from luc-github