Support for injectable routes and config (turn this module into a base package to be imported)

[vot]

This API should only provide generic endpoints and be extensible.

This package should be a base for cms-api instances and it should be imported as a dependency.
A separate cms-api-demo should become an example implementation so that upstream changes can be easily rolled out to deployed applications (by updating an entry in package.json).

ACs:

• this module should be exposing the API logic as an importable package
• when importing this package custom routes should be added to allow for extending of basic functionality as needed
• the base routes should remain here (pages, settings, user)