[PyCDE] Document basic functionality in 'tutorial' format and provide example code

[teqdruid]

• Document basics: modules, generators, system, ports, etc.
• Document the Type and Value systems. Discuss the difference between Python values and PyCDE Values.
• Document operator overloads,
• Document behavioral constructs.
• Ensure that said documentation is compatible with readthedocs.io.
• Create examples which are tested (via lit/cocotb/cosim) just like the 'tests'.
• Create a pipeline to rip out the testing code from the examples and publish them in the documentation. (Or vise versa.)