Replaced dependency on python-jsonmodels with internal module

The jsonobjects module was written to replace the functionality provided
by jsonmodels while offering the following advantages:

• More than 10 times faster
• Much lower memory footprint
• No need for manual validation
• Objects are validated on creation and everytime they are modified
• Guaranteed data consistency throughout the lifetime of the objects
• JSON arrays are first class objects allowing them to be used standalone
• JSON arrays can be embedded alowing for multi-dimensional arrays
• JSON arrays can define both item and array level validators
• Better semantics for optional properties and default values