Allow vendors to define their own actions. Actions were originally fixed-
length, which was a bit constraining. Actions now contain a length field,
which gives them more flexibility.
This cleans up the handling of modifying existing flows. There now exists
OFPFC_MODIFY and OFPFC_MODIFY_STRICT commands, which have the same matching
characteristics to their OFPFC_DELETE* counterparts. When adding a flow that
already exists, the counters and timers are now reset (ie, its treated as a
new flow). This commit also adds the "--strict" option to dpctl to allow
strict matching for "mod-flows" and "del-flows".
This has two notable omissions. First, only at most 4k of flow statistics
are reported. Second, aggregate statistics are not yet supported. Both
of these are fairly easily fixable, just not fixed yet.