Bug 7375 - Update minimum version of Perl to 5.10

Bug 7375 - Update minimum version of Perl to 5.10

- Change the installer script to look for at least 5.10/5.010000
- Change the template to ask for the correct version

To test:
- Run through the webinstaller on 5.10 or newer and check that there are
no errors.
- Ideally: Run through the webinstaller on an older version than 5.10 and
check that there *is* an error, asking for 5.10 or newer.

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>