Support timezone designator in timestamp string - fix Issue #58 - 4th try

Revision History
. Manipulate "-n 0" case to return start and end timestamps of a history facility directly, and improve client side API performance by taking advantage of this new feature;
. Sanity checks on the "-n" option;
. Timezone offset value should not be larger than "1200";
. Support documents with concrete examples;
. Re-send with the updated patches to support "00/15/30/45" in "mm" part of a timestamp string and a brief document under docs/ explaining the supported timezone format by C library strptime() API.