Starting to add new interact functionality
Incomplete modification of class behavior in interact_sagecell

This makes the interact control object responsible for its own value
and lets it control the values that will be passed from itself
to the interact function.
Updating the rest of the control types
More work on new interacts
Fix some more of the interact controls
Fixing issues with HTML controls
Renaming method; fixes to automatic_control
Allow interact control values to be retrieved and set

from within the interact function itself
Enable creation and deletion of interact controls
Add a _changed attribute to InteractProxy

with list of names of controls changed
Allow recursively-defined interacts on the same function
Allow an optional first argument to an interacted function

The InteractProxy will be passed through this argument
Only update interact from proxy after _update method is run
Add function sys._sage_.clear to clear output
initial namespace work
Keep track of all control value changes server-side

(including client-side changes that do not immediately update the interact)

This also simplifies the update system so that any control that triggers
an update will update *all* controls (rather than some pre-specified
set of controls)
Make created controls self-updating
Include single-underscore attributes in dir()
Use responsive grid layout for interacts
New “dirty control” style; bugfixes