Add support for the set-type-limit command in the ptop file.
It looks like this: set-type-limit <type> <count> This can be placed anywhere in the ptop file. It limits the number of physical nodes of a given type that an experimenter is allowed to use. For example, we may limit a user to 10 PCs, or 5 pc850s. In the latter case, if the experimenter had simply asked for 10 generic PCs, then we will try to find them some mapping of nodes that uses types of PCs other than pc850s. Added a precheck to tell the user up-front if they asked for more nodes than they are allowed to use of a given type.