Implement preset support in xjs.

[nelson-temporal]

Add preset support in xjs. Must be able to handle presets beyond the limit of current XBC UI.

[nelson-temporal]

Scene will have at the minimum

• [x] addPreset()
• [x] removePreset(Preset || uId)
• [x] switchPreset(Preset || uId)
• [x] getPresets() => Preset[]
• [x] get/set transitionTime
• [x] get/set transitionFunc