ScaleManager + DOM

"Final" changes for a solid 2.2-worthy ScaleManager.

This adds in official support for USER_SCALE, which allows a flexible way
to control the scaling dynamically.

It fixes a visible display bug in desktop browsers (viewport clipping was
off) and mitigates some potential issues all around by using a unified
visualBound calculations in Phaser.DOM.

It applies some protected/deprecated attributes, but does not remove any
behavior of already-established (as in, outside-dev) means.

There are no known [signficant] breaking changes; any known breaks (not
considered fixes) are constrained to dev with no known consumers.

Phaser.DOM

  There are no known significant breaking changes; Phaser.DOM was
  internal.

  - Added visualBounds; this should be the true visual area, minus the
    scrollbars. This should be used instead of clientWidth/clientHeight to
    detect the visual viewport.

  - Expose various viewport sizes as dynamically updated properties on
    Rectangle objects. These are visualBounds, layoutBounds,
    documentBounds.

  - Updated documentation the different bounds; in particular drawing
    distinction between viewport/layout bounds and visual bounds.

  - Renamed `inViewport` to `inLayoutViewport` to indidcate behavior.
    - Minor breaking, but dev-only

  - Changed `getAspectRatio` to work on Visual viewport. This will yield
    the expected behavior on mobiles.
    - Minor breaking, but dev-only

  - Removed some quirks-mode and legacy-browser special casing

Phaser.ScaleManager

  There are no known significant breaking changes.

  - USER_SCALE is 'made public'. It can used to flexibly configure any
    custom-yet-dynamic scaling requirements; it should now be able to
    replace any sane usage of manual sizing invoking the deprecated
    setSize/setScreenSize.
    - Added additional usage documentation and links to such
    - Added the ability to specify a post-scale trim factor.

  - Change the arguments the resize callback and document what is passed
    - Minor breaking, but the previous arguments were undocumented

  - `compatiblity.showAllCanExpand` renamed to `canExpandParent` and made
    generalized over possibly-expanding scaling.
    - Minor breaking, dev-only, for coding changing this settin

  - Switched from direct usage of of window innerWidth/Heigth to
    Phaser.DOM visualViewport - this change correctly accounts for
    scrollbars in desktop environments
    - Although it does slightly alter the behavior, this is a fix.

  - Removed usage of window outerWidth/outerHeight which didn't make much
    sense where it was used for desktops and was catostrophic for mobile
    browser
    - Although it may slightly alter the behavior, this is a fix.

  - Removed `aspect` and `elementBounds` because they are duplicative of
    Phaser.DOM (which can not be accessed as `scale.dom`).
    - Minor breaking, but internal methods on dev-only

  - Marked the minWidth/maxWidth/minHeight/maxHeight properties as
    protected. They are not removed/obsoleted, but should be revised later
    for more flexibility.

  - Orientation handling; non-breaking forward deprecations
    - Added `onOrientationChange` and deprecated the 4 separate leave,
      enter, landscape and portrait signals. They are not removed, so this
      is a future-migration change.
    - Fixed issue where state not updated prior to callback
    - Fixed issue where orientation callbacks were not always delayed

  - Fullscreen events: non-breaking forward deprecations
    - Added `onFullScreenChange` and deprecated `enterFullScreen` and
      `leaveFullScreen`.
    - Renamed (with proxy) `fullScreenFailed` to `onFullScreenError`.

Phaser.Device

  - Improved `whenReady` to support Phaser.DOM better
    - Allows a ready handler to be added without starting the
      device-detection proccess. This allows it to be registered to
      internally (eg. from System.DOM) without affecting current behavior.
    - Passes the device object as the first parameter to the callback
      function.

  - Fixed code where Silk detection not applied to `desktop` detection.

Manifest: System.Device moved before System.DOM