Bug 10646 - warn if mod_rewrite is not enabled

Bug 10646 - warn if mod_rewrite is not enabled

Koha requires mod_rewrite. If it's not enabled in Apache, then
koha-create will now abort with a helpful error message. Also adds a
warning when not run as root to avoid confusing errors.

Test plan:
 * apply the patch
 * a2dismod rewrite
 * run koha-create without sudo, note the error about being root
 * run koha-create with sudo, note the error about rewrite
 * a2enmod rewrute
 * repeat test above, note that it works

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Works as expected.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>