python: fixed iteration over removed entries
python: reformatted code
python: add check for zero disk_size
python: make blob.py more robust on headers mismatch

This also fixes `recover_index_from_blob.py` broken in:
    ddd07bee0ada42ebd54f355ccc309dc0fe3d7593
    "Make eblob.py more resilient to garbage in blob files"
python: do not siliently ignore errors
python: simplified sid()
python: added comments to blob.py
examples: recover: protect against inclusion
examples: recover: allow run under virtualenv
examples: recover: allow passing of data files via argv
python: improved error reporting
python: explicitly define header entries as longs
python: do not hang on errors
examples: recover: improve logging