Manually mounted feature

Created by: mguijarr

This PR adds the "Manually mounted" feature, it is made available thanks to a split button, instead of having just "Check sample changer contents" and additional dropdown allows to select "Manual mount". This disables ISPyB synchronization, and leaves the sample grid with only 1 sample, ie. the manually mounted one.

Question: the Queue has to be cleared, so I added a CLEAR_QUEUE action. I am not sure if this is the best way, since it just removes the queue on the UI side I guess it should be removed from the server too ? Or to switch to another queue ? I guess switching to another queue is better, if people want to come back to the previous queue they were doing before. Like, someone uses the sample changer, then puts a manually mounted sample, then comes back to using the sample changer... I think it is a legitimate use case.