Issue#23

Time stamps full support (with or without time zone). Major part of libpq inner timestamp decoding algorithm is ported.

Important notes:
* new feature: convert functions that can refer connection parameters (like TimeZone or integers_timestamps)
* connection and pool APIs are extended to handle meta information about time zone and time stamps format.
* small bug in asynchronous pool was exposed and removed (mistype in condition).
* time zone is used only for displaying data for an user. Internally time is stored in UTC.