Expose collection stats via API.
Expose database stats via API.

Update Backbone models to use stats instead of "size" rollup. This is going to make way for awesome.
Add collection size column.
Add detailed collection stats.
Add detailed DB size stats.
Fix remaining issues authenticating against single db.

Most were fixed in 43304335 but this seals the deal.

This change warrants a v2.3.0, so bumping that too!

Fixes #69
Fixes #74
Fixes #84
Fixes #91
Improve handling of invalid database names

Fixes #89
Clean up CHANGELOG
Bump version for 2.3.0
Merge branch 'release/2.3.0' into develop