PeakpickerHiRes: check if input is sorted, sort if necessary (fixes #892)

Checking/sorting is now done in the library (at one point), not in the TOPP tool (at multiple points). A flag allows to suppress both if the data is known to already be sorted.
The signature of the "pick" methods has changed, because the input can no longer be "const" to allow sorting. The alternative would have been to make a copy of the data for sorting, but ensuring const-ness didn't seem important enough to warrant this overhead.