check type of date fields in DictDB
fix a couple of datetime entries in the Hub
log exceptions in user requests in the Hub
catch KeyboardInterrupt in parallel tests teardown

because wtf Windows?
reduce test_cull_count test

it is slow, and didn't need to check so many times
monkeypatch RemoteError to include tracebacks during tests
allow datestamps to exclude microseconds

datetime.isoformat() excludes microseconds when the value is zero,
causing a 1/1000000 failure on most platforms, and 1/1000 on Windows due to millisecond datetime resolution.
update test_jsonutil

test previously failing case of no-microsecond timestamps

and update to use nt asserts instead of plain asserts

for better failure messages
Merge pull request #5098 from minrk/parallel-debug

mostly debugging changes for IPython.parallel