Unable to fetch a port number

When we fetch some port numbers, we could fetch only one port number because the port number was overriden. So we added another port valiables (r_port).
Merge pull request #49 from masanohashi/master

Unable to fetch a port number
fix an issue when add table-miss flow entry to flow table
fix issue #43
- added 'build learning_switch' to Rakefile
- deteled learning_switch.sh and Makefiles
fixed an issue #19 of parse_ether()
fixed issue #48
- update r_match_to_oxm_match()
- add pbb_isid_mask into Trema::Match
Added missing constants for group flows and table id's.
Merge branch 'fix-missing-constants' into wakame-edge