web: implement component editing

[dmlary]

For an existing component on an entity:

• [ ] be able to change fields
  • [ ] Simple types
    • [x] Entity
    • [x] single-line string
    • [x] multi-line string
    • [x] Numeric
    • [ ] Time
    • [x] Selection from valids
    • [ ] range limit from valids (maybe, feeling lazy)
    • [ ] Symbols (as strings in JS, but symbol in ruby)
  • [x] Arrays of a single simple type
    • [x] Add member
    • [x] remove member
  • [ ] Hashes
    • [x] delete key/value
    • [x] add key/value
    • [ ] set value type
    • [ ] specify hints/limits/etc
    • [ ] re-evaluate if we want to permit hashes as entity values (complicates things)
• [ ] be able to mark some fields as uneditable from the web interface
• [ ] limit value to field type if defined
• [ ] limit value to valid values if defined

[dmlary]

Alright, implementing this as PUT /component/<id>/<field>, and updating each field directly. This closely mirrors the behavior we experience in pry, and removes the difficulty of sorting out which fields were modified if we were to send all the values at once.

End UI will be editing a single field at a time. When save is hit, it propagates to the server.

We will need to open an issue for component generation counting to prevent web-interface from stomping on a component value that changed underneath them.

[dmlary]

Created ComponentFieldInput to handle all of this "magically"