Explore: Fix label suggestions for recording rules

Fix megacheck issues

$ gometalinter --vendor --disable-all --enable=megacheck --disable=gotype --deadline=6m ./...
pkg/tracing/tracing.go:81:25:warning: cfg.New is deprecated: use NewTracer() function  (SA1019) (megacheck)

$ gometalinter --vendor --disable-all --enable=megacheck --disable=gotype --deadline=6m ./...
pkg/services/sqlstore/user.go:274:3:warning: empty branch (SA9003) (megacheck)

$ gometalinter --vendor --disable-all --enable=megacheck --disable=gotype --deadline=6m ./...
pkg/tsdb/elasticsearch/response_parser.go:95:41:warning: should use make(map[string]string) instead (S1019) (megacheck)
pkg/tsdb/elasticsearch/response_parser.go:125:41:warning: should use make(map[string]string) instead (S1019) (megacheck)
pkg/tsdb/elasticsearch/response_parser.go:317:5:warning: redundant break statement (S1023) (megacheck)
pkg/tsdb/elasticsearch/response_parser.go:358:5:warning: redundant break statement (S1023) (megacheck)

append.

$ gometalinter --vendor --disable-all --enable=megacheck --disable=gotype --deadline=6m ./...
pkg/tsdb/elasticsearch/client/search_request.go:59:4:warning: should replace loop with sr.Aggs = append(sr.Aggs, aggArray...) (S1011) (megacheck)
pkg/tsdb/elasticsearch/client/search_request.go:303:4:warning: should replace loop with agg.Aggregation.Aggs = append(agg.Aggregation.Aggs, childAggs...) (S1011) (megacheck)

Explore: Query field fixes

Fix misspelled authentication in Auth overview doc

Don't use unnest in queries for redshift compatibility

Explore: Fix click to filter for recording rule expressions

- parsing of recording rules failed for label suggestor
- added ':' to parsing routine

- recording rule names contain ':'
- include this in the pattern for metric names

Fix megacheck issues

$ gometalinter --vendor --disable=all --enable=megacheck --deadline=10m ./...
pkg/tsdb/elasticsearch/client/client.go:147:13:warning: should use time.Since instead of time.Now().Sub (S1012) (megacheck)
pkg/tsdb/elasticsearch/client/client.go:190:14:warning: should use time.Since instead of time.Now().Sub (S1012) (megacheck)
pkg/tsdb/elasticsearch/client/client.go:218:13:warning: should use time.Since instead of time.Now().Sub (S1012) (megacheck)

$ gometalinter --vendor --disable=all --enable=megacheck --deadline=10m ./...
pkg/plugins/dashboards_updater.go:51:2:warning: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013) (megacheck)

$ gometalinter --vendor --disable=all --enable=megacheck --deadline=10m ./...
pkg/services/sqlstore/alert_notification.go:242:3:warning: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013) (megacheck)

disable codecov

removes unused files

Fix setting test

ref #11433

moves files from /tests to more appropriate folders

Moves docker/ to devenv/docker

Explore: Add multiline syntax highlighting to query field

* brian2222-patch-1:
  removes testdata from getting started
  Update getting_started.md