Create fieldplot.js

Most dependencies yet!

Adds the ability to add portals to a current "working set", automatically creating all possible non-conflicting links to all portals previously added to the set.

Portals can also be added by URL (in theory, untested).

When the set is "complete", ADA.FieldPlotter.plotField([cleanup]) can be called, to get a report of all blockers for all the links created between portals in the working set.  If cleanup is passed and set to true, it will also remove all the fake links that were created in the process.

The plotField function returns the working set, then creates a new one.  Sets aren't meant to be re-used.