Nat rule recertification

[abarz722]

for recertification of nat rules the preceeding rule selection has to be adapted.

• For that a checkbox "NAT rules" could be implemented in the left sidebar below the "Due within" field. Depending on this the respective report type is used.
• This checkbox could be suppressed by a default setting "NAT rule handling" (which could also be used for other NAT related features, e.g. appearance of the resp. default template)