Rhfogh mxcube3
Created by: rhfogh
Reverted change to AbstractSampleChanger, and various improvements in GPhL-specific code.
NOTE: The change to AbstractSampleChanger is a temporary fix that reverts a commit from 15/10. The modified version did not register a sample mounted from the samplegrid in app.CURRENTLY_MOUNTED_SAMPLE. Quite likely a more complex change is required to avoid reintroducing the problems that the previous change was supposed to solve.