Improve sort in TimeSeriesProperty

[wdzhou]

This ticket is blocked by :

• TRAC8685

TimeSeriesProperty uses stable_sort in method ''sort''. The flag to show whether a series is sorted is set to 'unsorted' if the sorted status is unsorted or unsure. For example, after add() operation, the flag is always set to 'unsorted' because it is unknown whether it is sorted with a new entry.

Sort() uses stable_sort, which is very costly if the vector is sorted while the sorting status is 'unsorted' for being unsure. This problem should be solved.

[wdzhou]

This issue was originally trac ticket 9244

[wdzhou]

http://trac.mantidproject.org/mantid/raw-attachment/ticket/9244/verify9244.py
(uploaded by @wdzhou on 2014-04-09T02:52:09)

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