Instrument specific Mantid.user.properties

[Pasarus]

Issue raised by: [developer/user/project requirement]

What?
We currently store some instrument-specific datasearch.directories in the Mantid.user.properties file. This is stored locally on our first compute node.

This is going to cause issues when we deploy more nodes because that file has to be maintained to be the same across multiple nodes.

A better approach would be to store that information in user/scripts/autoreduction for each instrument and load it either in the ReductionRunner or just at runtime in the reduce.py.

Another benefit of this is that it allows the users to configure Mantid directly (and potentially other software, so maybe user/scripts/autoreduction/configs is a good idea), rather than having to go through us to specify the newest required datasearch.directories (and other configs)