Merge branch 'testing-client'
Update tooltips displayed on ComponentCell
Set up variable for storing model labels

It's a TreeMap, which maintains sort order. Neato!

I added some dummy values to work with, for now.
Add worker method to LabelsMenu to populate menu

It uses a nifty Map iterator.
Set up framework to add new labels to a model
Set up framework to delete labels from a model
Refactor handlers for adding/deleting model labels
Add "Manage labels" button to MoreActionsMenu
Minor updates to comments and tooltips
Add available component names to model labels list
Select model label when driver is selected

When a component is selected as the driver of a model, also select its
label in the list of model labels.
Show labels unchecked when "Open" button selected

The instance of LabelsMenu used with the "Open" button should show all
available labels in an unselected state. The user can then check labels
to filter the list of available models to open.

Note that the selection state of the labels for the current model isn't
modified; the labels are only displayed unchecked in the LabelsMenu
widget.
Deselect model label when driver is deleted

This is the complement to when the driver is added to the model.
On login, set username as a model label

On logout, remove this label. (Alternately, uncheck this label. Need to
think about this.)
Include "public" visibility label

This label is unchecked (model is private), by default. On "Open", if
checked, all public models saved on the server will be visible. On
"Save", if checked, this model will be visible to all other WMT users.
Merge branch 'master' into testing-client