Merge pull request #182 from shaitan/master

Added common method for clearing and checking timestamp. Clears timestamp by -1/-1 by default.
tests: added prepare + append test case
eblob: improved logging in blob_write()
recovery: fixed spelling in docstring
tests: removed unused usage function
dnet: fixed timestamp (re-)initialization
dnet: set ts to mtime in write_file()
dnet: use half-open interval for key range checks
dnet: removed stale comment
Merge pull request #183 from SaveTheRbtz/master

Recovery: timestamp fixes and misc improvements
v2.24.13.9