Extra metrics to teacher dashboard

Summary:
The changes requested are rather simple most of the time. First of all there is a mirror copy of students, teacher, active_students, active_teachers for coaches who have less than 10 pupils. There is a lot of code reuse that could happen since we are tracking the same metrics the same way and just have to change filtering conditions. Furthermore there is tracking of class_profile view. It is achieved by filtering daily web request logs for class_profile and then finding whether any of those visits were our coaches. We can then plot time series using same function as for active_students! Also I have made coach_reduce more flexible to accept threshold. Due to this we can change definitions by just changing hive queries without touching python. I still have to confirm that this query actually does not have an error somewhere but initial tests don't show anything wrong. Later I will have a review with frontend changes for these new data points. I have moved the counting to a weekly job since it was taking too much time (extracting user_coach_date takes 8 hours where in my tests it took only 40 minutes - however checking past logs it seems that there must have been something wrong with my tests). Also now this job would take something in the neighbourhood of a day. If there's any renaming you would like me to do just ask.

way of computing counts for coachs and students in groups smaller than 10

I have no idea how it got here

add new fields to ka_hive_init version of student_teacher_count

include gae_bingo_identity when extracting entries from UserData. Used later for website visits mapping

add gae_bingo_identity to table definition

add job to track bingo_ids who visit class_profile urls on any given day

move teacher and student count to weekly job

add data series tracking usage of class_profile reports furthremore generalize coach_reduce to be able to use it regardless of tresholds

remove hive init

Test Plan: run the hive script

Reviewers: jace, chris

Reviewed By: jace

Differential Revision: http://phabricator.khanacademy.org/D2740