Moving a few things from dashboard folder

upgrade golang to 1.11.5

fix that alert context and result handle context do not use the same derived context.

* master: (262 commits)
  pkg/services/dashboards/dashboard_service.go: simplify return
  Updated url query param encoding to exctly match angular encoding
  Updated snapshot
  Added missing props not being passed to scrollbar component, fixes #15058
  Document /api/health
  changelog: adds note for #15062
  change default rotate_token_minutes to 10 minutes
  fix
  load test/ha fixes
  set low login cookie rotate time in ha mode
  fix multiple piechart instances bug
  scripts/build/*: Fix some golint issues
  scripts/build/*: Fix golint issues Url => URL
  build: fixes building grafana completely within docker.
  dont specify domain for auth cookies
  New snapshot reflecting changes
  Makes the clickable side menu header look great in light theme again
  org id fix for load test
  user auth token load tests using k6.io
  moves cookie https setting to [security]
  ...

pkg/services/dashboards/dashboard_service.go: simplify return

See,
$ gometalinter --vendor --deadline 10m --disable-all --enable=megacheck  ./...
pkg/services/dashboards/dashboard_service.go:167:2:warning: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013) (megacheck)

Updated url query param encoding to exctly match angular encoding

Added missing props not being passed to scrollbar component

Bug Fix #14961

Use CustomScrollbar in explore 

More file re-organization & clean-up

Document /api/health

Makes the clickable side menu header look great in light theme again

Document the health check implemented in #3302 (and #935), see  https://github.com/grafana/grafana/issues/3302#issuecomment-297066201

fix multiple piechart instances bug

WIP. POC for session replacement base hashed tokens.