ScaleManager - scaling consistency and bug-fixes

This includes some minor breaking changes.

- Unifies SHOW_ALL and NO_SCALE being stretched in Firefox and IE
  - As suggested by MDN: "..to emulate WebKit's behavior on Gecko, you
    need to place the element you want to present inside another
    element.."
  - This done via an (overwritable) `createFullScreenTarget` function.
    The (new) DOM element returned from this is placed into the DOM and
    the canvas is added to (and later removed) as the full screen mode
    changes.
  - MINOR BREAK: may affect code that assumes the Phaser canvas has a
    fixed DOM/CSS path (which should hopefully be nobody).  To use to the
    original behavior, where the canvas is not moved, simply set
    `this.fullScreenTarget = game.canvas` manually.

- Updates the refresh/queue to be unified and uses a smarter back-off to
  detect and react to parent dimension changes
  - Cleans up some odd browser issues; not tried on mobile
  - Fixes an issue were update might be called too much and spend time
    doing nothing useful.
  - `maxIterations` is no longer user and marked as deprecated
  - MINOR BREAK: previous approach would occasionally (but not always)
    back off updates the entire iteration/setTimeout sequence; under the
    new approach "onResize" may be called more frequently.

- Fixes a number various transition issues, mostly around RESIZE
  - MINOR BREAK, but correct: leaving RESIZE restores the original game
    size possible
  - Fixes assorted quirks with scales not being updated

- Layout
  - MINOR BREAK: All Canvas margins are "OWNED" by the ScaleManager. They
    will be reset in all modes as appropriate. This is for consistency
    fixes as well as coping with the updated full screen.
  - MINOR BREAK: Canvas right/bottom margins are set to negative margins
    to counter left/top margins. This prevents Canvas margin adjustments
    from affecting the flow .. much.
  - `getParentBounds` rounds to the nearest pixel to avoid "close to"
    value propagation from CSS.
  - Fixes page-align center pushing canvas out of parent

- Misc.
  - MINOR BREAK: `setScreenSize` will update the game size if the mode is
    RESIZE. User-code shoulde use `refresh` instead to ensure that any
    relevant changes are propagated.

- Corrected incorrect documentation
ScaleManager: more updates, fixes (eg. SHOW_ALL)

- NOTE: Changing `game.width/game.height` via user code was always
  problematic. This commit updates the documentation for such members as
  read-only. The only supported way to change the GAME SIZE after it is
  created is to use `ScaleManager#setGameDimensions`, which has been
  added.

- The GAME SIZE will be reset to the initial (or as set by
  `setGameDimensions`) values upon changing the scale mode or
  entering/leaving full screen. This may be a breaking from 2.1.2 (but
  many mode changes acted oddly prior).

- SHOW_ALL will now EXPAND it's parent container if it can. As per
  @tjkopena 's notes, this should more closely represented the expected
  behavior.
  - SHOW_ALL will first try to expand by the OVERFLOW AXIS and then
    attempt to resize to fit into the possibly larger area; use the
    parent's max-height/max-width properties to limit how far SHOW_ALL can
    expand.
  - RE-BREAKING: This changes the behavior from 2.1.4 and makes it more like
    2.1.3, with fixes.

- As per previous commit the ScaleManager _owns_ the margins and size of
  the GAME CANVAS. To control the dimensions of the GAME CANVAS, use the min/max
  height/width of the parent. Setting padding on the parent is _NOT_
  supported.

- Fixes various issues with switching between Scale Modes
ScaleManager: additional cleanup / fixes

- Sizing events:
  - CHANGE: The `onResize` callback is called only from `preUpdate` (which
    may be triggered from a window resize) and it will be called on
    refreshes even if the parent size has not actually changed.
  - A new `onSizeChange` Signal has been added. It is called _only_ when
    the Game size or Game canvas size has changed and is generally more
    applicable for performing layout updates.

- Game documentation now links to ScaleManager#setGameSize (which was
  renamed from #setGameDimensions)

- Removed extra/legacy full-screen restore code

- Margins:
  - Added `noMargins` flag; if set to true the Canvas margins will never
    be altered. This also means that
  - Margins are now set/cleared individually to avoid conflict with
    'margins' style compound property

- Code consistency updates
ScaleManager: back-port of "window constraints".

- Adds `ScaleManager#windowContraints`
  - In 2.1.3 and prior the scale modes (EXACT_FIT, SHOW_ALL) were actually
    based off the window dimensions, even though the parent element did
    not correctly reflect this nature.
  - When set (the default now is that right and bottom are set) the
    behavior will mostly correctly mimic the 2.1.3 (minus bugs) and
    before.
  - CHANGE (from 2.1.3): The window constraints also affect the RESIZE
    mode, arguably this is more consistent.
  - To disable this "constrain to window" behavior, simply set the
    appropriate property to false, as in:
    `game.scale.windowConstraints.bottom = false`
ScaleManager: (passing jshint)
ScaleManager updates and fixes

Conflicts:
	src/core/ScaleManager.js