Support more complicated default input values in create mode

[RFSH]

In the recordedit create form, we're populating the inputs based on the default value that ermrest reports. While ermrest allows and reports functions like now() in this property, ermrestjs/chaise only support simple raw values that conform to the column type. So now() is ignored by ermrestjs/chaise.

In this issue, we would like to explore the ability to allow more complicated "default" values. We don't necessarily need to use the default property that ermrest reports and could potentially do this by using annotations that only ermrestjs/chaise understand.

One thing that users asked for is the ability to populate date inputs with the current date. We should discuss whether any other functions (or computed values) we would like to support.