Increase in placables for cops and medics

This is just a general suggestion that placables amounts should be increased with every rank medics and cops receive

e.g. constable & senior constables could place 15 placables then sergeant and senior sergeant could place 25 placables. Acting as an increase with each rank. 

this would be a cool feature as it prevents placable abuse for lower ranks but allows checkpoints to be easily made and allows us to have a decent size checkpoint.