Update Temp Tower Post Processing

[GregValiant]

This is from a complaint on Reddit about the nozzle leaving a divot while it waits for the M109 to finish heating. This PR adds a relative Z+10 move prior to the temperature change and then a Z-10 back down to the working height after the M109 temperature is reached. Example:

G91
G1 Z10
M104 S220.0 ;AutoTowersGenerator: setting temperature to 220.0 C for this tower section
M109 S220.0 ;AutoTowersGenerator: Wait for the temperature to be reached
G1 Z-10
G90