[IMP] python examples: handle deletion in kvmsg.store
[FIX] python examples: fix issue with ttl=0 expiring immediately

in C examples, ttl=0 means do not expire.
[FIX] python examples: trivial sys.exit error in clonesrv6.py
[FIX] python examples: in clone.py, kvmap values are KVMsg not strings

This bug manifest itself with a stack trace when doing clone.get().
It seems to be present in the C code too?
Merge pull request #325 from lesbi/master

A couple of fixes to the python examples