AnimationPane has x_min and x_max attributes

[#52818341] These are calculated at to_json time if they can be inferred from the data set; otherwise they're set in the DB. (UI for that isn't done yet.)

https://www.pivotaltracker.com/story/show/52818341
Get x-max and x-min from derivative DataSets

[#52818341] If the DataSet is a derivative, we have neither expression nor data points; ask the original DataSet for that information instead. https://www.pivotaltracker.com/story/show/52818341
Update Hobo to 1.3.3

This was needed to ensure certain AJAX functions worked properly for [#52818341]
Refactor calc_min_x and calc_max_x to calc_range

[#52818341]
Additional model methods for AnimationPanes
WIP on updating the AnimationPane form dynamically