All responses of the web-annotation service are serialized to JSON.
But it is a JSON-API, so that limitation should be OK.
This was necessary since "<" and ">" in field values
would otherwise be escaped to entities.

- add output method to route.xq
- remove calls serialize in annotations and router module

BREAKING CHANGE: requires exist-db v5.0.0-RC8 or later

- replace deprecated functions

BREAKING CHANGE:
Batch update requests now MUST include a document key.
This is to filter the annotations that were
deleted on the client and therefore need to be
deleted on the server as well.

related:  https://gitlab.existsolutions.com/uni-heidelberg/ecpo/issues/2

- new module wap/request
- new module wap/request-parameters
- feature(router): allowed parameters for routes
- feature(annotations): batch annotations endpoint updates and creates
- add docblocks to most module functions
-

- add sample payloads to doc directory
- add example curl commands to readme
- all requests are now dispatched to route.xq
- application error handling
- updated to latest gulp-exist (scoped)
- POST /annotations/ can handle single and batch create (will fail on existing IDs)