Add MIB support for Lenovo Storage Array DE4800H series

Device support request for Lenovo Thinksystem Storage Array DE4800H (MIB attached).

The storage array and MIB are based on the NetApp E-series so there is already at least partial support. Additionally I think the attached MIB should be the same one used for each of these Lenovo series:

Lenovo ThinkSystem DE2000/DE4000/DE4200/DE4800/DE6000/DE6400/DE6600

Though the one we're actually running and able to test will be the DE4800H.

Attached snmpwalk file generated from:

$ snmpwalk -v2c -c 'librenms18' -t 3 -Cc --hexOutputLength=0 -ObentxU '192.168.137.13':'161' .1 > /tmp/myagent.snmpwalk

$ snmpwalk -v2c -c 'librenms18' -t 3 -Cc --hexOutputLength=0 -ObentxU '192.168.137.13':'161' .1.3.6.1.4.1 >> /tmp/myagent.sn

mpwalk 

Currently not much is configured on that host, but it is added to observium