As an admin of sonar I want to be able to drop a settings file on the sonar server, and define the path to it in the global settings, so that I do not have to copy paste the contents, which is errorprone

Acceptance criteria
- in the global settings of ReSharpePlugin there is a path property which I can set to the location of the file
- on restart it first looks for the file in this path, if defined, and load those settings.
  - it is ok to have no file
  - an error in the file should be logged as ERROR, but loading must continue
- then the string custom severities are checked
Moving things around.
Runs all tests
All tests pass