[add] speed.minimumSpeedMultiplier, for particles speed randomization

[zevlg]

To randomize initial speed for particles, speed.minimumSpeedMultiplier introduced in analogue with scale.minimumScaleMultiplier

Allows to create pretty blood-dripping-alike emitters, consider:

{
    "alpha": {
        "start": 1,
        "end": 0
    },
    "scale": {
        "start": 1,
        "end": 0.5,
        "minimumScaleMultiplier": 0.001
    },
    "color": {
        "start": "#992e41",
        "end": "#57010c"
    },
    "speed": {
        "start": 300,
        "end": 0,
        "minimumSpeedMultiplier": 0.1
    },
    "acceleration": {
        "x": 0,
        "y": 100
    },
    "startRotation": {
        "min": 180,
        "max": 200
    },
    "noRotation": false,
    "rotationSpeed": {
        "min": 0,
        "max": 0
    },
    "lifetime": {
        "min": 0.2,
        "max": 0.5,
    },
    "blendMode": "normal",
    "frequency": 0.0001,
    "emitterLifetime": 0.01,
    "maxParticles": 500,
    "pos": {
        "x": 0,
        "y": 0
    },
    "addAtBack": false,
    "spawnType": "point"
}

[andrewstart]

This looks good to me. I've been busy recently (and still am) but sometime I will find the time to make a release and add this into the editor.

[zevlg]

excellent, thanks!