Add support for proprietary HR ITCH186 server timestamps.

Signed-off-by: Alexander Laamanen <alexander.laamanen@valotrading.fi>
Add tests for the proprietary server generated timestamp.

Signed-off-by: Alexander Laamanen <alexander.laamanen@valotrading.fi>
Merge pull request #161 from valotrading/features/hr-itch186

Features/hr itch186