Add Arbitrary Property Storage to Each Shape

This feature proposes that each shape have a collection of arbitrary properties associated with it. These properties could be displayed and edited through a modal. A table within the modal would allow users to add/edit name/value pairs. This is incredibly useful for engineering diagrams, where additional properties might look like this:

repository: ws_code

owner: alix_owen

name: customer_create

payload: customer_info

status: completed

etc…