Alert user that a Microscope.JSON file with the same name already exists in the same Group

[strambc]

Is your feature request related to a problem? Please describe.
Currently, if a user attempts to save a Microscope a new MMA_Microscope Project will be created and a copy of the Microscope.JSON file will be created with the same name and ID in the Group.
This will create a conflict with other Microscope.JSON files with the same name that has to be saved by other users.

Describe the solution you'd like
Ideally we will have a SINGLE SHARED Project visible by all users in the group. This would avoid duplication.
In the absence of this provision (which might not be possible in OMERO), one solution is to issue an error upon Save to let Users know that another Microscope with the same name and ID is already available in the Group.

One could even go as far as tell the user that such new file cannot be saved.

Describe alternatives you've considered
Another solution is that Microscope.JSON files are kept outside OMERO in a dedicated repository.