changelog:
- changed layout and sequence numbering:
  * layout: ethernet header | timestamp | seq id | block 0 + CRC | 0xcafe + inter-frame seq_no| block 1...
  * the seq_no is per-frame, internally, there is internal sequencing, first
    block is considered 0 but has only seq_no, not sub-frame seq_no, the latter
    blocks have sub-frame seq_no
- added legacy generics
- debugged