Store configuration for baselayers in Config.groovy.

Since this config rarely changes, it makes sense to have it in the more static Config.groovy rather than the DB, with the benefit that it's one little bit less state to be stored in the DB, and a removal of the need to re-configure every existing portal instance to use the new baselayer URLs.
Coding style
Rename 'configuredbaselayers' -> 'configuredBaselayers'.
Merge pull request #1044 from aodn/baselayers_in_config

Store configuration for baselayers in Config.groovy.