G cloud bug fixes

Some bug fixes for G-Cloud. 

1. Wording changes following discussion with Phil
2. Add missing stub option to match main dashboard
3. Related links should use relative paths and not open in new tab
4. Fix hover and date display bugs on completion_rate graphs by simply removing null data from the series. 
5. Stop x-axis labels overlapping 

Pull requests for point 4:
https://www.pivotaltracker.com/s/projects/911874/stories/64157358
and hopefully will fix: 
https://www.pivotaltracker.com/s/projects/911874/stories/64158244

Pull request for point 5: 
https://www.pivotaltracker.com/s/projects/911874/stories/64157584