Support simple dynamic code for number and string props

[itsdouges]

Common methods of declaring some props are to use simple math, for example rotation and using Math.PI. To make using these kinds of prop declarations easier Triplex needs to support:

1. Updating props with "code"
2. Declaring the code in the prop controls

For (1) currently you'll find Triplex only supports updating primitive values / arrays. It should also support arbitrarily setting "code". We may already be able to do this with no changes, need to explore.

For (2) declaring the code in prop controls will need a more advanced input to be built that can switch between "primitive" and "code" view. And ideally the code side also needs to "on-rails" so it can't be given invalid options.