Changes for Auto-Leveling & Blank LCD Issue

This will make Auto-Leveling work better, and also allow for easier
Repetier-Host & Slicer Configuration.

Also changed UI_START_SCREEN_DELAY to 4000 (This seems to help the blank
LCD issue.)
Fix Nozzle Cleaning

There was an issue with nozzle cleaning function that will cause the
nozzle to hit the bed.

This is caused by the memorized position being set to 0 before homing,
which is then changed to -30 after homing, which caused the nozzle not
being returned to the proper position.
Fixed Position Menu LCD Corruption.

I forgot to change the number of menus when I removed the X,Y,Z Homing
in a previous commit, which caused the LCD to display corruption in the
"Positions" menu.