Add system initialization code for tests

It sets up UART and external memory.
Add readback test

This test writes values to CC registers and memory and reads it back for
verification.
Add CC register definition include file

Register definitions hould match the verilog include file registers.vh in
the chronocube project.
Add tile and sprite register definition includes
tests: Add landscape test

This test tests both sprites and tile layers.  It is meant to be an
exhaustive test of the current CC rendering capabilities.