Added Date Filter, Priority Filter, and Filter Reset (ITS#182)

[rpike@labs.gte.com]

I am presently polishing up my changes to Jitterbug 1.6.2 which I hope to
have uploaded soon.

1. Added age filter to select messages older or newer than the specified
number of days and tidied up 
    filter pane including addition of a "reset filter" button.The date
filter works well along with the priority 
    filter to get all high or urgent priority messages older than n days.

2. Enhanced Darren Gonzales' Priority Feature:
   a. Generalized to use a character array to set priority list. Setting
the default setting is still awkward. 
       It should be an easy modification to read this list from a
"priorities" file like users, if someone has a 
       good idea how to specify which item is the default.
   b. Added Priority checkbox filter and cleaned up match_message logic
slightly.

3. Finishing up a "taken by" feature (as opposed to the usual
"assigned_to") so that a registered user can 
    claim an issue if no one else has already claimed it and unclaim it
when complete or so someone else 
    can work on it.  Others users can see who, if anybody, has claimed an
issue.  There is also a filter option
    for this. Anybody have a better name than "taken by"?


For the priority feature, I used a looping technique to dynamically create
and process cgi variables which could 
be used as a model for the addition of any variable length list item (such
as STATUS).

For the priority checkboxes, I used a power of 2 bitmask to carry the state
of the checkbox to avoid adding too 
many variables. 

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Richard Pike                               Email: rpike@labs.gte.com
GTE Laboratories Incorporated      Phone: 781-466-2689
40 Sylvan Road, MS 61                Fax:     781-466-2712
Waltham, MA 02451-1128
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