move scene logic to components (fixes #239, #759, #886)

[ngokevin]

Scene components:

• canvas - Controls creation or selection of a canvas render target.
• stats - Handles RStats.
• keyboard-shortcuts
• vr-mode-ui - Handles VR UI (button/modal).

Scene modules:

• fullscreen - Handles fullscreen events.
• iframe - all the postmesage stuff
• meta-tags - Handles injecting of iOS metatags.
• wakelock

Additional changes:

• AEntity - HTMLElement.setAttribute to DOM for default components for scene.
• canvas - Height/width configurable, triggers a render-target-loaded event on scene for scene to set up renderer.
• look-controls - Point canvas to scene canvas.
• stats - Put the UI within the scene.
• Remove ?vr URL parameter, not sure if it is being used or actually needed in the core.
• vr-mode-ui - Can be disabled. Put the UI within the scene.

Tested:

• Some unit tests for new components
• Macbook Pro on Firefox/Chrome. Enter/exit VR work for Firefox, modal is thrown on Chrome as before
• On iPhone 6, enter/exit VR and orientation modal work as before

[caseyyee]

Fullscreen events should be ignored when vr-mode is forced to VR? Stereo rendering resets to mono when exiting fullscreen.

[ngokevin]

I pushed my updated changes to this PR. Moved fullscreen stuff to https://github.com/aframevr/aframe/pull/776/files#diff-344cbe83c2f901ba50d1f8824d89ccfeR18

So you want the use case to always force stereo and completely ignore fullscreen events?

[caseyyee]

Not sure, debatable I suppose. my thought was that if you are going to manage your own viewport rendering, then you would want to also manually handle fullscreen events as well.

[ngokevin]

I'm a bit confused. Are you suggesting that if vr-mode is forced to VR, then ignore fullscreen events? And how should we allow vr-mode being forced to VR?

[ngokevin]

Okay after what must be a good week of working this, this is ready.

[dmarcos]

Can we set those to empty string so they're not defined for every entity?

[ngokevin]

Updated. Moved fullscreen/metatags/wakelock to modules. Added keyboard-shortcuts scene component.

[dmarcos]

Are these changes related to the intent of the PR?

[ngokevin]

Yeah wanted to expose the scene components in the DOM