Parse older log files for cv loads

 - For older files, have to match on 'checksum-verifier' rather than
   'cv_plugin'

Version:   2014.1211.1
Change-Id: I9e5f855c2154196a890910033711648857ce0178
Add option --dry-run to 'crawl history'

 - Ignored for 'crawl history --show'
 - For 'crawl history --reset', reports table name (with prefix), database
   name, and host name.
 - For 'crawl history --load, reports table name (with prefix), database
   name, host name, and filename for cv records.

Version:   2014.1211.2
Change-Id: I0fab8cc9d124be5851bf161f8f7b8f28df6af9be
Allow the user to select the history report format

 - Added argument to option --show for 'crawl history'
 - Updated history_show() to accept the user-specified format and use it
   to select the appropriate history report routine
 - Adds routine history_show_raw(), which supports 'crawl history --show raw'

Version:   2014.1211.3
Change-Id: I1c0790acb0d082c6e162031da9c7e7290f73d943
Low level tweaks to support history reporting

 - add error messages
 - util.ymdhms() - accept an option format to allow the caller to control
   the format of the date returned
 - update crawl_lib.retrieve_history() to allow the caller to specify the
   arguments to db.select()

Version:   2014.1211.4
Change-Id: I685b617454fc09d4b894cdbe2d7d8e03e99c37e3
Add 'crawl history --show count'

 - Report hits by plugin

Version:   2014.1211.5
Change-Id: I83e70ea00427684c7e3661ae95612ce5a7bcb136
General time period code

 - To generate a time-period report, history_period_show() just needs a
   MySQL format indicating the desired period.

Version:   2014.1211.6
Change-Id: I92f516f4a2ad3bbc176864150d9fe4f8e291a8ba
Add 'crawl history --show byday'

 - Report hits by date by plugin

Version:   2014.1211.7
Change-Id: I3836c33dbd25ec6b6c6c65d41ff62099628c9238
Add 'crawl history --show bymonth'

 - Report hits by month by plugin

Version:   2014.1211.8
Change-Id: Ib6abd936442900dfa241921a3cc6efbbf3f40903
Allow reporting history by week

 - 'crawl history --show byweek': Report hits by week by plugin
 - Uses wk2ymd() to go from week number to the date of the Monday in the
   week, which depends on datetime and timedelta, so those modules had to
   be imported

Version:   2014.1211.9
Change-Id: Ifc7e2212521115e4397e728c1022c4f47f1fe778
Merge branch 'history'
Release "Visible"

 * New features
    - History reports by day, month, week, count, or raw
    - Load history from plugin tables (tcc, mpra, rpt) and log files (cv)
      back to the beginning of time
    - Added --dry-run option to 'crawl history' so operations can be tried
      out non-destructively

 * Maintenance improvements
    - util.ymdhms() now accepts a format so its default can be overridden
    - History report format selection uses introspection so a new format
      can be added simply by writing the function. There is no need to add
      it to a list or register it in some special way.

Version:   2014.1217
Change-Id: Id4d99c282dcd91849acb4513b0bd9207ec17911f