David  Dec 19 2007
    - May as well start keeping checkin notes for Bolt.
        At this point the fundamental structure of Bolt is
        more or less complete, I hope; many features are missing.

    Items for this particular checkin:

    - Make things work right when you resume a course at an
        exercise answer page.
        This creates a new View, whose prev_view_id link points
        to the exercise view, not the answer page view
    - When leave a page using "Up", terminate the view accordingly.
    - Rather than using $_GET, Form vars are now passed to exercise primitives
        in a global variable $bolt_ex_query_string, which they must parse.

    db/
        bolt_schema.sql
    html/
        inc/
            bolt_db.inc
            bolt_ex.inc
        user/
            bolt_course.php
            bolt_sched.php

David  Dec 27 2007
    - preliminary implementation of exercise_set

    inc/bolt.inc

David  Jan 1 2008
    - split control structure into separate files
    - allow passing query strings to items

    db/
        bolt_schema.sql
    html/
        inc/
            bolt.inc
            bolt_rnd.inc
            bolt_seq.inc
            bolt_xset.inc
        user/
            bolt_course_sample.php
            bolt_sched.php

David  Jan 17 2008
    -  Add table for selects

    db/
        bolt_schema.sql
    html/inc/
        bolt_db.inc

David  Jan 30 2008
    - implement the review mechanism

    db/
        bolt_schema.sql
    html/
        inc/
            bolt_db.inc
            bolt_xset.inc
        user/
            bolt_sched.php
        
David  Jan 31 2008
    - finished and mostly debugged the refresh mechanism

    db/
        bolt_constraints.sql
        bolt_schema.sql
    html/
        inc/
            bolt_select.inc
            bolt.inc
            bolt_db.inc
            bolt_xset.inc
        user/
            bolt_map.php
            bolt_sched.php
            bolt.phph
            bolt_compare.php

David  Feb 1 2008
    - Add Bolt admin page
    - added "hidden" flag to courses

    db/
        bolt_schema.sql
    html/
        inc/
            bolt_db.inc
            bolt_ex.inc
            util.inc
            util_ops.inc
        ops/
            bolt_ops.php
        user/
            bolt.php
            bolt_sched.php

David  Feb 6 2008
    - implemented question mechanism

    html/
        inc/
            bolt.inc
        user/
            bolt_course.php
            bolt_sched.php

David  Feb 7 2008
    - fixed bugs in review and repeat

    html/
        inc/
            bolt.inc
            bolt_rnd.inc
            bolt_select.inc
            bolt_seq.inc
            bolt_xset.inc
        user/
            bolt_sched.php

David  Feb 8 2008
    - removed "bolt_" from API functions.
        I don't think this prefix is useful;
        Bolt isn't going to be used within large existing PHP code

    html/inc
        bolt_ex.inc

David  Feb 22 2008
    - added sketchy implementation of Maps

    html/
        inc/
            bolt.inc
        ops/
            bolt_map.php

David  June 26 2008
    - (a bunch of checkins recently)
        Added basic Unit Comparison feature, including
        - snapshots (makes it fast)
        - filtering and breakdown
        Also revisited Maps, and started redoing them along the same lines