Enforce one name for quantity states

[NoisyFlowers]

Currently, creating a quantitative state is handled just like any other state: the user can enter the name for the state.

We need to only have one name for quantitative states, so we can identify them as such. The form should have a checkbox for quantitative, which disables the name field.

[NoisyFlowers]

This is in 6b934bb.

Keeping this open for now because I want to remove the check I added to include "quantitative" as well as "quantity" as the node name.