Add recusrive syntax checking for additionalItems

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>
Move AdditionalItemsSyntaxChecker in the proper package

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

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>
Recursive syntax checking for additionalProperties

Also rename the test.

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