Change "Search metrics" to "Find metrics"
Remove 'refresh available metrics' button (link still in action)
Use global setting to disable tooltips, leave on by default
Remove default tooltip setting in  development
Correct issues with nose dive data, NaN data on stacked graphs

For a metric with σ = 0, it would appear as having no y-axis. This is corrected.
For a metric with σ = 0 and x̄ = 0, it would appear as having no value nor axis.
This is corrected.

Logic regarding how to handle a lack of data in descartes dataset padding is
corrected, and handled in rickshaw: the nil value is used in the controller,
which is explicitly handled in rickshaw to cast back to a NaN