FlxMouse: add getters for justPressedTimeInTicks

[adrianulima]

Added getters for times in ticks of mouse button inputs, also made comments more consistent.

This makes FlxMouseButton#justPressedTimeInTicks accessible on FlxMouse, it is useful on cases we want to know how long a button was pressed.

if (FlxG.mouse.justReleased)
{
	var timePressed = FlxG.game.ticks - FlxG.mouse.timeJustPressed;
	trace(timePressed < 500 ? "Mouse click" : "Mouse long press");
}

[Gama11]

This property is already exposed for FlxTouch - the naming should be consistent:

flixel/flixel/input/touch/FlxTouch.hx

Line 35 in fd190e8

public var justPressedTimeInTicks(default, null):Float = -1;

Also, I just noticed we use Floats for ticks in FlxTouch / FlxSwipe / FlxMouseButton, but ticks is an Int... I can't think of a good reason for that, it probably results in a loss of precision.

[Gama11]

Opened a separate issue for the Float / Int thing: #2071

[adrianulima]

@Gama11 I saw it is public for FlxTouch and it's equivalent for mouse is FlxMouseButton that is already public and consistent. I thought that FlxMouse was more like FlxTouchManager, that don't have this field, but allows user to access directly FlxTouch objects.

So since we can't have access to FlxMouseButton in FlxMouse, I added it there.
The reason to have a different name was on purpose. I thought in a different start of the property to avoid code completion showing them first when user type "presse..." or "justPresse..." and avoid confusion with the other bool properties.

But I can change it to justPressedTimeInTicks to keep consistency even at FlxMouse level, which names do you suggest for Right and Middle ones?

[Gama11]

justPressedTimeInTicksMiddle and justPressedTimeInTicksRight seems like the most consistent naming.

I'm actually not a huge fan of how this API works, I'd prefer if you did have to access the values through the mouse button instances:

FlxG.mouse.left.pressed;
FlxG.mouse.right.justPressed;
// etc

But I doubt we'll change that anytime soon, seems unnecessarily breaking.