ts: How will we handle tskit nucleotide/integer position vs. float position vs. AlphaSimR marker position?

[gregorgorjanc]

tskit ecosystem used float position coming from coalescent simulations. Then there was a switch to nucleotide/integer position, which is now the default.

AlphaSimR uses 1:nMarkers for marker positions, but stores genetic map in SP object and recombinations are done in the genetic map units (as float/double I believe).

We will need to find a way to work across all these "units".

Now sure what SLiM does, but given how popular it is, we should ensure that our solution works with all these tree sequence generators.