Improve PropNValue.contains().

[fhermeni]

This used to run in O(n). Given the array is read-only, it is ok to sort it and use Arrays.binarySearch() to perform in O(log(n)).

For an internal benchmark with 128 values to watch, contains() was the bottleneck (5% of the service latency), now it is < 1%.

[jgFages]

Thanks Fabien !