Fix linelabel test following matrix collection removal
Shift linelabel requirement from base graph to grouped graph so it is only loaded when needed
Use last defined value for line graph labels when last values are null
Remove summary related code

It's changing in https://www.pivotaltracker.com/s/projects/911874/stories/73142060 to only show the date, so the existing stuff is redundant
Stripped down stacked line label tests to only test what has been extended
Remove redundant options from grouped-graph config