make blast scriptable

[ugjka]

Add these flags:

[ugjka@ugjka blast]$ blast -h
Usage of blast:
  -bitrate int
        mp3 bitrate (default 320)
  -chunk int
        chunk size in seconds (default 1)
  -debug
        print debug info
  -device string
        dlna friendly name
  -headers
        print request headers
  -ip string
        ip address
  -port int
        stream port (default 9000)
  -source string
        audio source (pactl list sources short | cut -f2)