Add 'local' features and desires. As opposed to 'global' fds, these
effect a single node, but are different from 'class' fds in that they are stateful - ie. the socre you get depends on all other vnodes currently mapped to the pnodes. These are identified by prefixing them with a '?'. ('*' for global, mnemoic 'matches all'; '?' for local, mnemonic 'matches one') The currently implemented local fd is the additive one, or '?+'. We add the desire weight for all vnodes on the pnode together, and if this number is greater than the pnode's weight for the feature, a violation is flagged. The idea here is that we can give a pnode a feature like: ?+memory:256 and vnodes desires like ?+memory:16 or ?+memory:64 to pack vnodes onto pnodes in a manner that appropriately reflects their resource usage.