[TECH SUPPORT] LPS-34567 Site template page import causes ConstraintViolation

Hi Tamás,

I have applied the following changes:
- added init param for SecureFilter to avoid PrincipalException because of the missing permissionChecker
- added logic to reset the merge fail counter on the Site Template when the user wants to reset the changes on an inherited Site page. With this modification the reset feature will still work when we have a friendly URL collision between other pages in the same site

Please review my changes.

Thanks,
Ákos