Add min and max times to load balance plot

[rsdunlapiv]

Is your feature request related to a problem? Please describe.
The load balance analysis right now only shows total times, i.e., for each timed region it is the total amount of time spent in the region, accumulating all of the iterations of the region. You cannot determine from the total time if some executions of the region where significantly faster/slower. E.g., often the last execution of a region is more expensive, since there could be extra work involved, such as writing a file.

Describe the solution you'd like
The load balance plot should have several options:

• total time
• min time (fastest execution)
• max time (slowest execution)

The user should be able to switch between these options and have the plots refreshed.

We like will need separate JSON data files - one for each of the stats above.