Add a Ring conformation choice to the GAG builder on glycam.org

Is your feature request related to a problem? Please describe.
The old gag builder on legacy is able to create the various ring forms of DIdoAp. After the user clicks on an algycone to finish the sequence you get a Ring Conf(conformation) option:

After clicking on Ring Conf, you can only pick DIdoAp residues. This is what we want.

Then after clicking on one you get a menu for 1C4, 4C1 or 2SO. If you click on one of these it alters the sequence like so(note that I edited two residues here:

Describe the solution you'd like
We should add this ability to the new one at glycam.org/gag. The functionality to handle this at the gmml level exists in the juggle_testBranchFreeze branch of gmml. So once that's merged into gmml-test it should all work.

Bonus: Before you click to select an algycone there is no indication that you can manipulate the ring form, so making that easier/clearer would be nice. When the user clicks on IdoA it might be nice if a ring conf box appears that they can optionally click on and inject the e.g. (2SO) into the string.

Extra info
In the near term future (~years) we won't want to do this for residues other than IdoA, but this may get applied to some other residues at some point.