added options to dhcp_agent.ini

* This adds comments to the INI
* dnsmasq max lease
* allows metadata network access on 169.254.169.254/16
* allows for debug to be set

New attributes have been set as defaults
added notification driver support
fixed typo

I added notification topics, I made a typo: /nova/neutron/
Merge pull request #86 from cloudnull/notification_driver

Merged automatically by jenkins after successful build test