Making it possible to indirectly access the registers via constants.

Adds OBP0_ADDR and OBP1_ADDR to the list of registers.

There's a new rust stable version.

Support for some basic Python testing.
Handling of loading error with proper error propagation.

Also made some initial timer validation.

Test for test_blargg_instr_timing.

This allows background to take precedence over objects.
This completes the CGB ACID 2 test compliance.

Created infrastructure that allows the usage of the serial device to capture the result of the tests.
Then the test is executed agains a pre-defined number of cycles and the result is compared against expectation.