Added cron job to send unsent scheduled emails every 5 minutes

I've used puppet to set up a cron job that sends unsent emails that
are scheduled to be sent every 5 minutes
Added the ability to un/release specific comments for rubric evaluations

This is the first commit for allowing instructors to un/release specific
comments of a rubric evaluation (similar to what can be currently done
with rubric evaluations).

Included in this commit is:
* modifications to the sql scripts (include upgrade scripts) to include
an attribute to mark whether each specific comment is released
* buttons to "Save changes" of releasing the selected comments
* buttons to "Un/release all" comments for an evaluatee or the whole
group
* internal check to mark a group_event as reviewed if all of the
evaluation_details in the group has been modified after the close
date of the evaluation - in other words, the detail was marked as
released or unreleased using Save Changes or un/release all (or
combination of both).

Along with this additional feature we have remodelled the process of
un/releasing evaluation results, which is described below. We also
took into account the possibility of an instructor changing the
auto-release attribute BEFORE and AFTER the close date of the event.
* BEFORE close date
   * grades/comments release links/buttons would not be visible, to
     remove the ambiguity of whether the results have been reviewed
   * if auto-release is turned on, evaluation details are defaulted
     to have comment_release/grade-release=1
   	* they are set to zero if auto-release if off
   * if the auto-release status is changed during this period, all
     submitted evaluations will be marked appropriately
	* eg. from off to on - mark all release status to 1

* AFTER close date
   * grades/comments release links/buttons would be visible
   * if auto-release is on, students can see the results as soon
     as the evalution results start date has been reached
   * if the auto-release status is changed during this  period, all
     submitted evaluations will be marked appropriately IF the
     group event is not marked as "reviewed".
	* if the group_event is marked as reviewed, no changes to
          the release status of the details would occur, because
          we assume the instructor has reviewed the comments and would
          like to keep those changes.
modified student view of rubric evaluation results

The student view of the results for rubric per evaluations has been
modified to reflect the individual releases of comments that were
made possible on the instructor's view of the same results.

To make the view more readable:
- I have made the grades (including titles) not visible if they are
not released. Reason behind this decision is if we couple that with
some comments being unrelease, we will have a long list of "n/a", which
discourages students to read the results.
- I have also made the student view of their own evaluation grades/comments
for their team members to be visible whether the grades or comments have been
released or not. This is the same behaviour from before.
    - consequently, comments are not filtered in this section, I'm assuming
      the student knows what they wrote (whether it is good or bad)
made modifications to the functionality of releasing indiv comments

- only displaying buttons to release comments and grades after the
event has closed
- chagned release all comments/grades to only change release status
of evaluation rubric entries that are not "reviewed"
- updated controller and model tests to reflect the changes made to
some of the functions for the releasing individual comments feature.