Add old German radars `deflg` and `desna` to OPERA radar database

[peterdesmet]

In BALTRAD, there were data submitted for the following two radars that are not listed in the OPERA radar database:

• deflg (data until 2018)
• desna (data until 2019)

I don't have more info about these radars, except for what I can find in the vp data:

deflg

source: NOD:deflg,WMO:10908,RAD:DL81,PLC:Feldberg
interval: 200
levels: 20
lat: 47.8736
lon: 8.0036
height: 1516
minheight: 0
maxheight: 4000

desna

source: NOD:desna,WMO:10873,RAD:DL82,PLC:Schnaupping
interval: 200
levels: 20
lat: 48.1747
lon: 12.1018
height: 677
minheight: 0
maxheight: 4000