add predicate CounterPred and effect CounterEff

[samuellsk]

The purpose of this is to have simple counter and have a control over it. For example counting 10 creatures and if less than spawn 1..
if i have 7 furniture do...

Filter CounterPred less/more/eq "name of counter" 10 {
CounterEff "name of counter" increase/decrease/setto 1
}