Start some prep for fine-grained events (#329)

* Start some prep for fine-grained events

* Fix build/test targets

* Tidy bash scripts

* Update notes

* Delete dead test/nginx_stub/ dir

* Add docker-compose volume-mount overlay for faster dev loop

* Fix rubocop warnings

* Simplify ExternalSaver

* Delete dead comment

* Look into create bash script to create populated v2 group

* Add light.previous_index in rb code rather than js code

* Delete dead comments

* Put previous_index property into light in gatherer.rb

* Start create_v2_dashboard written in ruby

* Fix rubocop warnings

* Add more comments

* Update comments

* create_v2_dashboard now creates group

* Delete dead comment

* Fix rubocop warnings

* Add kata_ran_tests() to external_saver

* Add kata_create_file() call to create_v2_dashboard.rb

* Get first traffic-light in create_v2_dashboard.rb

* Dont use predicted:nil

* Use predicted:'none'

* Add called to external-differ

* Fix create_v2_dashboard.rb call to kata_create_file()

* Update notes

* Update rubocop config file

* Update test metrics limits