Add agent scheduling for LBaaS namespace agent

- adds simple chance scheduling on create pool operation
- adds PoolsLoadbalancerAgentBinding db table
- adds lbaas_agentscheduler extension to list pools hosted by a particular agent
  and to get an agent hosting a particular pool
- adds agent notifiers mapping to AgentSchedulerDbMixin to make it easier
  for services to add their agent notifiers to the core plugin

Implements blueprint lbaas-agent-scheduler
Change-Id: Id98649fd5c7873dcd5be1a2b117b8bed25f06cc2
Avoid refreshing firewall rules unnecessarily.

Adds a parameter to refresh_firewall allowing an array of ports to
be passed.  If an array is passed then the firewall will be refreshed
only for those ports.  If not passed, it will still refresh all
ports as it did before.

Change-Id: I539a135dbc3861e31cbb5c69cef0ff8c0f834527
Fixes: Bug #1202328
Imported Translations from Transifex

Change-Id: I2c8877e5987b5251bf59680d77c281dde895e58c
Merge "Avoid refreshing firewall rules unnecessarily."
Add help strings to Config Options

Add an help string to the config options

Change-Id: I9248a335db961aa5d776a545dcfba0ddb0f08bb2
Imported Translations from Transifex

Change-Id: Idb25d3056791dced787695f8dea4720b8652235a
Merge "Imported Translations from Transifex"
Imported Translations from Transifex

Change-Id: Ieabd6279524cbb26c3ae093550840f13c0e584f0
Merge "Add agent scheduling for LBaaS namespace agent"
Merge branch 'master' of https://github.com/openstack/neutron into opendaylight