To avoid WASM serialization issues.

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.

Allowing better directory usage.
Created initial printer file.

The complete GB, CPU and MMU linking is done.

Also added CH4 public WASM API

Also fixed small channel 3 issue

Support for set of video, audio and timer.
Now with support for toggling audio in the SDL version.

This is specially useful for disabling APU if not used.

Using a dequeue it's possible to control the size of the queue and outdate old elements.

There are a series of hacks involved in making a constant stream of audio data to work OK with web audio.

These are temporary fixes.

Made use of queue support for SDL avoiding the callback approach which greatly simplifies the code and increases the APU accuracy.

It's stil glitchy and noisy, need to check the problems.

Still requires work to be able to be able to emulate APU together with the CPU instead of inverting the control.

This a very work in progress situation that requires stability.
The most important part is the fact that it's possible for an external entity (SDL) to call an audio tick and get a volume.

Uses built package to print dependencies.

Normalized handling of ticks in SDL according to the Web version implementation.

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.

Related to #7

Related to #7