Schemavalidator

Disable error table output

Only render debug info on log level debug.

Add option to validate against custom schema objects.

Added `validate_json_string` method to validate json strings.
This is especially useful if your project uses a custom json encoder or if you work with raw json strings.

From this version on all id's and rerences need to be absolute.
Id's and references have to be absolute with respect to the base schema
path. So with the following file structure:


schemas/foo.json
schemas/sub/bar.json


The ids and $refs will become `/foo.json` and `/sub/bar.json`.

This is a breaking change.