Improving model modules, implementing core server fixture, and using it to get the first functional tests up and running.

- Migrating more DTO stuff into the core-java model module.
- Splitting the model out of folo common, and creating folo client api module
- Creating aprox-test-fixtures-core to hold new core server fixture, to aid in functional testing
- Attendant changes to Vert.x booter to help the core server fixture function correctly
- Improved first functional test that checks store admin CRUD operations, via the core-java client api
- Improved core-java client api as needed to pass functional tests for store CRUD ops
- Added logic to write out default configurations from classpath resources to etc/aprox/main.conf and etc/aprox/conf.d/ if these don't exist on boot