Corrects handling for 1.03 and 1.04 repbeats

1.03 stores the repbeat waveform data in the element text, while 1.04 has a subelement <waveform> to store the actual data. Also, it appears from the comments in the 1.04 schema that the repbeats could be compressed. Tentative support to determine what the compression is and to early out is provided.