Add alerts to debug run response code of 0
Add method to locate open children of parent item in model tree

ModelTree#findOpenModelCells(TreeItem parent) returns only the open
ModelCells of the children of the parent. This is different than
ModelTree#findOpenModelCells(), which used Tree#iterator to walk the
tree, and which dives all the way down each branch before proceeding to
the next.
Add ModelJSO#nComponents method

This is the same GWT issue that bit me earlier: JsArray#length returns
0 in dev mode but null in production mode. Use this nComponents method
instead.
Add another saved model test case
Use HTTPS for all calls to the API

Not doing so violates the same-origin policy, and we need HTTPS for
transferring the username & password for the host on which the model is
run.
Fix error in parsing uuid from run/new server response
Minor progress in refactoring model deserialization

Oy, what mess.