- Removed redundant query to analytics_predict_samples
- Analysers API now uses recordsets to iterate through the analysable
elements. They take the last analysed time into account.
- New method for targets so there is no need to always update the last
analysis time. Useful for lightweight targets.
Added new parent class for targets that use course as analysable and
student enrolments as samples. course_dropout target was modified to
extend that parent class.
This was done for indicators, targets and time splitting methods so that we
can get the string identifier and component in order to display a help_icon.
The functions were also made abstract, removing the default implementation.
Indicators, targets and time splitting methods should define this function.