Group - 'iterate' documentation and guard

Update iterate documentation to cover usage of `args` and added a guard so
that the callback can be used without requiring that `args` is specified.

Ref. https://github.com/photonstorm/phaser/issues/1352
Group - additional documentation refinement

General tidying/corrections of Group documentation.
Minor logic fix for Sprite life update

The substraction of `physicsElapsedMS` needs to be done for all individual
updates. (When current FPS ~ target FPS this is a 1-1 mapping, but catchup
updates can throw off the calculations.)

Also renamed `Game#updateNumber` (a poor initial name on my part) to
`currentUpdateID`. This matches the naming of
`Stage#currentRenderOrderID`.
Sprite - removed comment

The comment was no longer valid after the previos changes.
jsdoc - PIXI documentation filtering

Added the filterpixi.js jsdoc plugin which marks some PIXI
interaction-related methods and properties as private. This ensures that
they do not show up in the final Phaser documentation.
jsdoc - added namealias

The namealias plugin gets jsdoc to detect lots of documentation it was not
correctly picking up due to the application of the `name` property. This
can be read about in
https://github.com/jsdoc3/jsdoc/issues/804#event-195287680 - this results
in _much_ more complete documentation generation, especially when
properties are defined in constructors.
jsdoc - short/friendly @link plugin

Added support for short `{@link #member}` markup. This makes interlinking
much cleaner and shorter; similar short-link support was available in
previous versions of jsdoc.
jsdoc - sourceproxy docs and cleanup
jsdoc - namealias fix

Fixed issue with namealias and class doclects without names.
Documentation - general

Updated some documentation for formatting, consistency, and minor
corrections.
Documentation templates - edited resource entries

Added Game and Particle entries.
Documentation - consistency updates

- Updated `readOnly` doclet to `readonly`

- `array` refined to `type[]`, where such information was immediately
determinable.

- Updated {Any}/{*} to {any}; {...*} is standard exception

- Udated {Object} to {object}
Documentation - typo fix
General docs - reverting src/pixi changes

(Because outside of control, really.)
Documentation - Group

- Merged in group doc updates

- Added a DisplayObject stub type for better link-out across documentation
Documentation - number refinement

Changed some {number} types to {integer} where such is trivially
verifiable.
Documentation - Signal
Event-Signal object count optimization

There are a bunch of signals added for Sprites; more when input is
enabled. However, very few of these signals are ever actually used. While
the previous performance update related to Signals addressed the size of
each Signal object, this update is to reduce the number of Signal objects
as used by the Events type.

As a comparison the "Particle: Random Sprite" demo creates 3200+ Signals;
with this change there less than 70 signals created when running the same
demo. (Each Event creates at 8 signals by default, and there is an Event
for each of the 400 particles.) While this is an idealized scenario, a
huge amount (of albeit small) object reduction should be expected.

It does this by creating a signal proxy property getter and a signal
dispatch proxy. When the event property (eg. `onEvent`) is accessed a new
Signal object is created (and cached in `_onEvent`) as required. This
ensures that no user code has to perform an existance-check on the event
property first: it just continues to use the signal property as normal.

When the Phaser game code needs to dispatch the event it uses
`event.onEvent$dispath(..)` instead of `event.onEvent.dispatch(..)`. This
special auto-generated method automatically takes care of checking for if
the Signal has been created and only dispatches the event if this is the
case. (If the game code used the `onEvent` property itself the event
deferal approach would be defeated.)

This approach is designed to require minimal changes, not negatively
affect performance, and reduce the number of Signal objects and
corresponding Signal/Event resource usage.

The only known user-code change is that code can add to signal (eg.
onInput) events even when input is not enabled - this will allow some
previously invalid code run without throwing an exception.
Merge pull request #1389 from pnstickne/wip-event-signal-redux2

Event-Signal object count optimization
Merge pull request #1385 from pnstickne/wip-jsdoc-core2

jsdoc core/plugins