Config contains idType to set default for application

[andys8]

Summary

It is possible to define idType (by default "integer") per service. This PR adds an optional param idType to the root configuration object. The value is the default but can be overwritten.

• The changes are backwards compatible.
• I added the param to the test. I'm not really proud of the way it is, but there is a test. A test setup with multiple instances would be an option in the future, but adds complexity (failed shutdowns, timing, ports).