Add support for SNMP

[stakach]

Provides two services

1. SNMP modules (control of devices over SNMP)
2. SNMP status (for monitoring the control system using existing tools)

Existing projects that will be useful

• https://github.com/normelton/snmp4em
• http://www.cuddletech.com/blog/pivot/entry.php?id=588
• https://github.com/hallidave/ruby-snmp