Update to json-schema-core 1.1.5, lots of changes

* All keyword validators/format attribute validators use a message bundle.
* Add the syntax and validation message bundles to ValidationConfiguration.
* Modify many constructors accordingly.

Also modify examples 8 and 9 to add some messages. Takes care of one part of
issue #55, but lots of work is left to do.

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>