Use 128-bit GUIDs instead of 16-bit profile IDs

[wavesoft]

It might be a better idea to use GUIDs for the profiles instead of a pre-assigned 16-bit integer. The overhead is not big if you consider that it will appear only once in the header.

[wavesoft]

The profile ids can be placed either on S64 or on S8. On compact bundles this makes no difference, but sparse bundles need to load the separate s64 stream in order to identify a possibly invalid configuration.

Since dependencies are also not defined it might be a good idea for a new header structure or for some streaming meta data.