Split dock to allow swapping upper part

[EiNSTeiN-]

I'm working on modifying some parts to accommodate a Rapido UHF hotend. The Rapido UHF is longer, so it requires this mod which adds 8.3mm of length to the Stelathburner front plate. And in turn it moves the screw holes 8.3mm up from where they are supposed to be located when the toolhead is docked.

I added a simple 0.05mm split in the dock body so the dock can be printed in 2 parts, this will allow swapping the upper part for a new one. I think this is a useful change to allow the creation of new upper parts for different toolheads or magnet configuration if necessary.

[EiNSTeiN-]

Printed and tested:

[viesturz]

Nice, thanks for all the work!