Change `CBASS` `obs` and `var` to `row` and `col` consistently

[michaelweylandt]

@agenevera wants us to change "obs" and "var" to "row" and "col" throughout since the notion of "observation" and "feature" might not apply wherever bi-clustering is used. This is not a hard change to make, but we should do it after we decide whether to use $X$ or $X^T$ internally throughout, since working with $X^T$ will make it very hard to keep "row" and "col" clear in the code.

Let's wait until the technical documentation (#28) is complete before deciding how to proceed.

[michaelweylandt]

Closed by #51