Add support for Benning MCU3000 UPS devices

Hi! We are in the process of replacing our older Delta USVs with new devices from Benning. Unfortunately, they are currently not supported in observium, so we went ahead and implemented support.

Find attached:

• the snmpwalk result as requested in https://docs.observium.org/developing/add_device/#snmp-dump
• a patch (p0) that adds the implementation we came up with, which includes the vendor's MIB file as downloaded from the web interface of the UPS
• 2 logos, which are scaled-down versions of the logo included in the official press kit by benning, where it is provided as EPS to the public. i do not have written permission from benning to use the logo, so please don't sue me, but i guess it counts as fair use? not sure how you handle that stuff.

if you need anything else or i can help in any way, please let me know.

thanks!