Scatter coach reports now report all listed statistics.

All statistics re-enabled in coach reports api views.

Timeline coach report restricted only to items for which we have timestamps that make sense.
Use human readable names on scatter coach report.
Prettify axes labels.
Standardize data input to scatter and timeline coach reports.
Merge branch 'release-0.10' of github.com:learningequality/ka-lite into coach_report_Stats_and_UserLogs
Total User activity, and User Activity over time on coach reports.
If user logging is enabled, then user activity coach reports are now available.

The Timeline coach report now automatically selects the correct y-axis value based on the selected time attribute.
Removed debugging code. Removed unnecessary JS files in coachreports.
Small fix - syntax error in Javascript.
Merge branch 'release-0.10' into coach_report_Stats_and_UserLogs

Conflicts:
	kalite/coachreports/api_views.py
Merge branch 'release-0.10' into coach_report_Stats_and_UserLogs

Conflicts:
	kalite/coachreports/api_views.py
Resolving weird merge cruft.

Change use of settings to UserLog.is_enabled()
Increase left margin on scatter plot and timeline graph to prevent axis tick label cut off.
Prevent Y-axis drop down from showing any options in timeline coach report.
Merge pull request #600 from rtibbles/coach_report_Stats_and_UserLogs

Reinstating and fixing all coach report stats, and enabling User Log stats when enabled