Add the basic Transform system and stubbed transform resource

It is a singleton type object that can retrieve an entity's transform.
Added TransformSystem unit tests
Merge branch 'feature-transform-system' into develop
Changed transform test source files to be inline with other test source files

Also renamed transform_system.hpp/cpp to transform-system.hpp/cpp
SerializerBase::Serialize now takes a document instead of just a value

This is done because adding members to a value requires the allocator.
This can be obtained from a document.

Also moved TransformSystem into the system namespace.
TransformSystem can now serialize and deserialize to JSON

main.cpp calls GetInstance() on Transform and Resoruce system
to register them with JSONParser.
JSONParser now knows how to save to disk