fix loci OXM ordering to match the spec

The C backend will now output OXMs in the same order as the Java backend.
openflow_input: fix naming of group type in group desc stats entry

The C backend blacklists the name "type" so accessors aren't generated.
"group_type" works and is consistent with the other classes.
Merge into master from pull request #86:
Remove unnecessary prefixes from Value Type constants (https://github.com/floodlight/loxigen/pull/86)
Merge into master from pull request #88:
fix loci OXM ordering to match the spec (https://github.com/floodlight/loxigen/pull/88)
add bsn_flow_idle extension

Similar to standard OpenFlow idle timeouts with a flow-removed notification,
but does not remove the flow.
Merge into master from pull request #89:
openflow_input: fix naming of group type in group desc stats entry (https://github.com/floodlight/loxigen/pull/89)
Merge into master from pull request #90:
add bsn_flow_idle extension (https://github.com/floodlight/loxigen/pull/90)
java_gen/DataPathId: make comparable