don't depend on user's current date display format

If the current user's date display format is RFC2822 (e.g. "Mon, 15 Dec
2014 18:19:28 +1100"), pressing "+1d" may not correctly result in the
date advancing by 24 hours.

This seems to be a current limitation of the RT web interface's date
parser.

Enforcing the outputted new dates to be in ISO format (and thus not
relying on the user's display preference) seems to fix the problem.
enclose first top button in Perl loop

The remaining buttons in the top row will be built by this loop
shortly.
use Perl to build "+2d" button
use Perl to build "+3d" button
use Perl to build "+1w" button
use Perl to build "+1m" button
enclose first bottom button in Perl loop

The remaining non-resetting buttons in the bottom row will be built by
this loop shortly.
use Perl to build "Monday" button
add option not to stall when changing Starts date
add option not to show top row of buttons
read bottom non-resetting buttons from config
allow "reset" button to be renamed/hidden
ensure correct URL when no operation occurs

Clicking on the "reset" button when the ticket already has no Starts
date results in nothing occurring, but the browser URL loses the ticket
ID, resulting in a URL which couldn't be bookmarked.

Explicitly specifying the ticket ID in the query string of every form
submission solves this problem.
fix POD
add contribution information
Merge pull request #1 from Lx/Lx-config-options-and-bug-fixes

config options and bug fixes