fix filtering bug in Interactive Browser page
default page titles: Lab Interactive <Browser>

When Interactive is loaded add: ": <interactive.title>"
handle case where there is no model JSON link

This occurs when there is an error loading the model
JSON and there is no valid path reference.
energy2d: support stepForward, stepBackward, isNewStep

The energy2d model does not include support for the
model tickHistory yet so stepping backwards is not yet
possible.

However stepForward is possible.

The function stepBackward is a null operation and just returns
the current step counter.

isNewStep() always returns true.
finish moving managing the title to application.js

… and embeddable.js
add importedFrom to interactiveController.serialize()

I'm now using the existing controller.serialize() method
for getting the loaded interactive and have removed
access to the interactiveController.interactive variable.

FIXME:
The serialize() function needs to be updated so this kind
of manual copying from the metadata isn't necessary.
energy2d: curricular versions of HTB: S1A1, S1B1