Move server configuration settings from the database to the config.xml file

[johnsaigle]

There are certain configuration settings that will break LORIS when changed, e.g. base, and url. They shouldn't be editable from the front-end.

The decision was made in a recent meeting to move these fields to the config.xml file instead of the database. This has the result of overriding anything the user enters in the front-end thus fixing the issue of someone accidentally breaking LORIS.

This will also allow developers to edit fields via the configuration file rather than establishing a connection to the database.

There are likely other fields (host?) that should also be moved to the config.xml file.

Further discussion is required as to whether e.g. file upload paths should be moved too.