Use Transmitter instead of Source address, support 4addr frames

When we analyze the RSSI we are actually interested in the Transmitter (TA),
not in the Source (SA)... Change to generally use TA instead of SA, and RA
instead of DA.  Reviewed TA/RA usage against the standard (802.11-2012).

Also add support for 4 address frames (ToDS and FromDS is set), the TA address
change is mostly relevant in this setup (WDS, wireless bridge).
Allow one node to have more than one mode

Use MODE as intended, as a bitfield, allowing more than one mode per node. E.g.
an AP may also use WDS at the same time or an Adhoc node may send Probe
requests.
better display of encryption (ENC)
STA copy RSN, WPA from AP

We can't get this info from looking at the STA frames only, where just the
encryption bit is set and we don't know wether this is WEP or WPA... As it is
connected to the AP it has to use the WPA from the AP.
upload: reset average also for nodes which we don't send