Improve Welcome Game Collision and Controls

[BRNMan]

When I first considered enable3d for my project, I played the welcome game on the website and came away with an unfair impression of the project because the player would phase into a lot of the geometry in the scene, and the controls were not complete.
For example, the player can step underneath this ox at the beginning, which made me wonder if the collision worked:

This commit should mitigate some of the collision jank by making the player's bounding box more accurate. It also adds left right and backwards movement so the player can move around like a normal game and increases the jump reset timer.

[yandeu]

Thanks a lot. Look great!

[yandeu]

Actually, a capsule shape is even better. I have change it.