add support for array parameters

## As a USER, I can create ~~hashes and~~ arrays that are sent in requests as JSON ~~objects and~~ arrays

### Acceptance Criteria
1. User can specify ~~`hash` or~~ `array` as parameter types.
 - ~~If `hash` is a type, sub-parameters are expected in the definition of the object.~~
1. When a variable has type `array`, the UI allows the user to add as many fields as they'd like.
1. ~~When a variable has type `hash` or `object`, the UI creates input boxes for each sub-parameter.~~

### Tasks
- None

### Additional Notes
- Related: https://github.com/synapsestudios/synapse-common/pull/1

Underscore has an isFunction method.