Rickshaw graph: use y-minimum, even if it's negative.

From https://github.com/shutterstock/rickshaw/issues/10#issuecomment-4731953

If the minimum y point is negative, without specifying this parameter, the
mininum will be forceibly set to 0.

Why? Maybe "They were just thinking positive." -_-
Update Rickshaw.Fixture.Number.js to glasnt/rickshaw:round-y-axis-tick-label version
Use rounded y-axis ticks
Set pixel tick space to 30 pixels (down from default 75)
Have metrics return data results, source lists return list of metrics available
Add alias into the settings for each backend type
Add dynamic searching to descartes
Descartes needs to know it's alias as well
Add a bit of back padding to start date for descartes

With forced interpolation, ensures that the data for start exists.
Move backend helper to application layouts (one method to rule them all)
Add backend helper to application helper.

Force use of bigfilter metrics
Plus some formatting issues
Cleanup graph controller

Move to no cached metrics assumed
Cleanup superfluous code
Change caching logic for backends

use redis keys, not smembers, for searching
by default, search by redis

define a separator function (NOT global, needs work) to define a separator for
backend and metric name
Define list function for metrics (searching for metric names)
remove case statement that shouldn't happen
No more assumed cached metrics, so no more case checking
Remove ui message for checking metric cache list (no longer valid)
Use dynamic searching for metrics, not static rails-generated multi-selects
Remove advise re cached metric count (no longer valid)
Add helper script to parse that a descartes URL is working as expected

Usage: gimme a url, i'll give you dataz