Add support for new implementation class

[cjmyers]

There is partial support of a prototype that James created, but it should be moved to use SBOL Implementation once formally approved.

[cjmyers]

Need to create a form for creating an implementation to collect metadata for the implementation, the Agent who built it, the Plan (with attachments, possibly a zip file) used to build it. Should be able to select if this will go into a new submission or an existing one in your private repository. This is accessed by GET request on /createImplementation.

This information should then be used with a POST to /createImplementation which creates the Implementation, creates the Activity, and links the Implementation through the Activity to the CD or MD that has been built.

Need to create an Implementation page.

The button to createImplementation should appear on CD, MD, and Implementation pages.

[cjmyers]

Implementation view page added in PR #757. Should still consider adding (or updating) the functionality to create implementations.