general: Elasticsearch logging with Lumberjack.

* Added disabled-by-default config options for Elasticsearch logging.

* When Elasticsearch logging is configured, don't populate rnkPAGEVIEWS and
  rnkDOWNLOADS.

Signed-off-by: Joe MacMahon <joe.macmahon@cern.ch>
WebStat: register custom events on es

* Adds `loanrequest` schema for `Lumberjack`.

* Adds custom events elastic search logging.

Signed-off-by: Harris Tzovanakis <me@drjova.com>
Merge remote-tracking branch 'cds-ops/pr/87' into prod

Conflicts:
	requirements.txt
Merge remote-tracking branch 'cds-ops/pr/88' into prod