fix and adjust statistics system

[DJ2LS]

statistics are actually broken - lets fix them

[DJ2LS]

{"callsign": "OH2JRB-0", "dxcallsign": "ZZ9YY-0", "gridsquare": "KP11HN", "dxgridsquare": "------", "frequency": 14093000, "avgsnr": 0, "bytesperminute": 0, "filesize": 215, "duration": 29.880011081695557, "status": "FAILED", "version": "0.16.2-alpha", "time_histogram": {}, "snr_histogram": {}, "bpm_histogram": {}}

Stats are showing wrong call sign.

[DJ2LS]

dxcallsign should be fixed now

[DJ2LS]

server site should be okay for now with introduction of constants file