[RFC] Prototyping speed improvements

## Problem
Prototyping in amethyst is slow.

100 lines of code seems to be the minimum to make the smallest of game. While its not a lot, it definitely is more than necessary.

## Source
I'm taking https://github.com/amethyst/amethyst/blob/develop/examples/sphere/main.rs as a model
Lack of good defaults for generic types.
Imports
Lack of handle_event utils for simple cases -> Quit on any key, quit on some key, is key pressed.

## Propositions
>Lack of good defaults for generic types.

Adding sensible defaults as type alias for generics.
1) Add a default.rs file.
2) Make a DefaultSomething type alias with a default consistent with the others.
3) Export the module default.

Example:
amethyst_input/src/default.rs
```
type DefaultInputHandler = InputHandler
```

>Imports

Expand the prelude to include as many common types as possible. I'm not too sure how much this slows down compile time when using the prelude, but I do have performance degradation in one of my project where I was using only preludes.

>Lack of handle_event utils for simple cases -> Quit on any key, quit on some key, is key pressed.

I already implemented it inside of a custom project, currently debating if this should be inside of the engine.