Add parsing of gorouter logs to custom_filters
Add parsing of gorouter logs to custom_filters

We want to parse the fields in gorouter logs so that they can be more
easily filtered by request fields, client ip, etc.

This change adds grok matching for the request lines where
@source.component=gorouter.

Ideally we would also add the relevent lines for the index mapping too
but it was not as simple to extend this part of the elastic search
config from the manifest directly (and this is also the case for the
uaa_nginx and vcap_haproxy lines) so we have left that for now

alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf