Reduce code redundancy

- Use multiple print;
- Use say for print line;
- Add helpers for fetching ENV values.
Fix graph title spelling
Monitor server admins and users amount
Fix markup
Fix typo
Fix invalid vlabel for CouchDB request times graph
Better couchdb_httpd_requests graph

On big green area background other metrics lines are more readable.
Revert AREA to LINE for couchdb_request_times graph metrics

It was a mistake since the last area overlaps all previous, so their
values aren't visible on graph.
Don't stack couchdb_auth_cache metrics
Monitor databases docs count and fragmentation
Provide back references for project repository
Don't duplicate warnings content
Better autoconf
Update notice about side effects