refactor port binding codes

Bug #1195047

This patch:
1. removes the iteration in get_ports to call extend_dict_binding
2. uses a unified way for plugins to do this kind of stuff

ml2 will enhance the binding so that it can have different binding
for port according to port's host.
mlnx and bigswitch are also exceptions due to the dynamic binding info.

Change-Id: I5a77eb7395e14482a856e033f536f72a1bf82e06
Delete useless and wrong comments in NEC Plugin

This commit deletes useless and wrong comments in NEC Plugin, and adds
_clean_nec_ini() to Cleanup to make sure it is called.

Fixes: bug #1208716
Change-Id: I5c7950617cdf5d66f5f5cf3334bf2d5e617148eb
Cisco plugin db code cleanup, part II

Remove an unused table.
Prefix Cisco tablenames with cisco_.
Make full use of neutron model base class.
DRY out the nexusport binding queries.
Follow coding guidelines for imports.
Improve cisco/db/network_db_v2.py test coverage.
Improve cisco/db/nexus_db_v2.py test coverage.

Change-Id: I8ea110de37552176f2d9bcbff4ca3e0b65dfacdc
Closes-bug: #1202687
Partial-bug: #1190619
Imported Translations from Transifex

Change-Id: I9fd1c6211c108e110b4d299af62677e6dc0889fc
Merge "refactor port binding codes"
Merge "Delete useless and wrong comments in NEC Plugin"
Merge "Cisco plugin db code cleanup, part II"
Remove metadata_router from init

Remove references to metadata_router from init so that the
Neutron server starts properly.

Signed-off-by: Ryu Ishimoto <ryu@midokura.com>
Remove metadata references

Remove metadata router references from plugin.

Signed-off-by: Ryu Ishimoto <ryu@midokura.com>