IPAddressWithMask should have a contains method taht can take any IPAddress
add exception test
fix null NPE catch
return false for incompatible ip versions
add bsn_action_checksum extension
add bsn_require_vlan_xlate extension
add bsn_vlan_xlate_port_group_id extension
Merge into master from pull request #293:
java_gen: make of_bsn_log a string (https://github.com/floodlight/loxigen/pull/293)
use preconditions
Merge into master from pull request #287:
LOXI-55: IPAddressWithMask should have a contains that can take any IPAddress (https://github.com/floodlight/loxigen/pull/287)
Merge into master from pull request #292:
Add a few new TLVs (https://github.com/floodlight/loxigen/pull/292)
change checksum combination operation to addition

Addition/subtraction has advantages over XOR in that two adds of the same value
don't cancel each other out, and the high bits are better utilized.
Merge into master from pull request #294:
change checksum combination operation to addition (https://github.com/floodlight/loxigen/pull/294)
java/HashValue: add+substract, remove combineWithValue

The HashValue types gain arithmetic add and substract operations. Also
removes the obsolete combineWithValue operation that had weird/broken
semantics.