minor changes to mac_learner
Refined syntax to add Filter policy class
renamed aggregate queries from the cryptic counts/sizes to the less cryptic count_packets/count_bytes
added match_modify policy
slight enhancement to pyretic.py
name change that should have been in previous update
added EthAddr and IPAddr as type names
don't need tmp variable
add dropped_by policy
fixed typo
added aliases
moved dropped_by to its proper location - as a basic combinator
removed dynamic decorators - IMO more confusing than anything elset
optimized if_ evaluation
renamed vdefs
fixed up _print and removed complicated debug stuff from virt library