run basic integrity check prior to full up  (dae/anki d2535fd)

This commit omits any code in the UI that handles changes in the full sync result.
 catch notes with invalid field count in db check (dae/anki 7ad33fe)
 modding the schema should also set collection modified (dae/anki 84a03d2)

required for the force full sync case
Update sibling/burying behaviour to be in line with Anki 2.0.14.

Includes only changes to collection.py in these commits:
rework sibling handling and change bury semantics (afde116)
unbury on open for now (a2463eb)
unbury on open/close and make sure we set usn when unburying (0bef1d8)
 we can remove graves when uploading and save space (dae/anki e9ab912)