[pftools] Water Balance Closure Tool: Simplified View

[jaredwhite547]

Hydrologists want to tell at a glance if their water balance is closing. To do this, a time series scatter plot should be displayed showing the error over time. Two lines, showing +- 0.005% error should also be shown. In the future, this error range should be user-adjustable.

User Story: As a hydrologist, I want to quickly check if my water balance is closing, so I can know if my domain is correct.