Added ELV WS 2000 weather station sensors
Fix sample rate handling The former DEFAULT_SAMPLE_RATE 48000 was upped by librtlsdr to 1024000. Now it's possible with "-s 250000" to reduce the CPU load to a quarter.
Frequency hopping "-f" can be given multiple times, e.g. "-f 433761931 -f 868198412". After 2 successfull decodings or 10 minutes, whichever happens earlier, the program tunes to the next frequency. This way, both ISM bands can be decoded with 1 stick.
EM 1000: cleanup
Frequency hopping: #defines