Bug 16760: fix Circulation Statistics wizard under Plack

Bug 16760: fix Circulation Statistics wizard under Plack

This patch fixes some variable scoping problems when running
the circulation statistics wizard under Plack.  For example,
when using the item type as a row header, with this patch the
item type description is displayed rather than "UKNOWN VALUE".

This patch also enables warnings and fixes a couple variable
initialization issues. (Note that turning on warnings across
the board would make it easier to identify Plack variable scoping
issues, as "Variable "$foo" is not available at' errors would
be recorded in the Plack error log).

To test
-------
[1] Run the staff interface under Plack.
[2] Go to the Circulation Statistics Wizard and run a report
    using item type as the row. Note that the row labels
    display as "UNKNOWN VALUE" rather than the item type.
[3] Apply the patch and restart Plack.
[4] Run step #2 again; this time, the item type descriptions should
    be used as the row labels.

Signed-off-by: Galen Charlton <gmcharlt@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>