Make plot functions capable of generating their controllers

Currently, plot functions in plotting.py accept a data dictionary and a bokeh figure to plot to. Some plots required their own UI elements to adjust plot settings. It would be preferable if the plot function generates these UI elements and returns a bokeh column that contains both the plot and the UI control.

Plan:

1. update existing plots to receive only a data dictionary, and return the bokeh container object that is most relevant
2. update plotting.plot_signal_vs_bvec to create required slider