Allow simple screenshot saving.

Support for MBC3 and MBC5 in state.
Renamed dumps and loads methods.

Using static methods instead of global functions.

Game Boy color was still being mentioned, even though it was already implemented.

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

The solution makes use of the chrono module to obtain time and the image module to save PNG files.
The Web version is still pending support for printing.

Uses the `build.rs` file to generate compile time information about the build environment.
This information is exposed to the WASM environment through interface methods that are then used by the `Emulator` interface.