Bug 13452: 'Average loan time' report to obey item-level_itypes preference

Bug 13452: 'Average loan time' report to obey item-level_itypes preference

Fixes the 'Average loan time' report so that the system
preference setting item-level_itypes is taken into account.

Before the patch, the report was always using the biblio
level itemtype. With the patch, it will depend on the pref
setting.

To test:
- Run various reports, compare results with both
  possible pref settings
- Try limiting your search in various ways, especially
  on a specific itemtype
- Make sure you switch checkboxes in testing,
  using itemtype as the row or as the column

Notes:
- Filtering on a specific itemtype on master was not working
  if the itemtype was chosen as column. The patch should fix that.
- Fixes headings and breadcrumbs so that the name of the report
  is the same as on the reports start page

Signed-off-by: Indranil Das Gupta (L2C2 Technologies) <indradg@gmail.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>