Support timezone designator in timestamp string - fix Issue#58 - 5th try

Revision History
. historyAppend supports NO records with a timestamp equal to the last one;
. Improve how the start and end timestamp of a history facility are fetched;
. 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.