Add y-sorting to the TargetArray class.

[yosefm]

This step needs to be performed after detection if the result is to be used in OpenPTV-Python for tracking and other stuff. The tracking algorithm does target searches. It assumes they are sorted on Y so it can do a binary search.

I used to do this phase inside my correspondences binding, because that's where it starts to matter, but it shouldn't be there, and the correspondences binding I'll eventually contribute will be much simpler than what I have now.

[alexlib]

Simple and clear. recommend to merge.

question - when we do two tests - do we need to do the same test in binded version and in the C version?

[alexlib]

the tests pass

sorting on the Y coordinate in place ... ok

[yosefm]

We don't necessarily have do the same test twice, but sometimes the simplest way to test the binding is to check that it does what the C version does. Only calling it to see that it runs through is not enough because some input/output errors in the Python/C/Python chain will run through but give back garbage. In this case, there is no way to check that the method actually does something except to check that it did something.