[r] add IterableMatrix-Methods examples

[immanuelazn]

Add examples for every IterableMatrix method together in the IterableMatrix-methods.Rd.

Using a super simple example of transforms on as(matrix(1:25, nrow = 5), "IterableMatrix"). One thing that I'm thinking is it might make sense to have the examples show the result as a dgCMatrix instead, as the stdout doesn't necessarily show how the numbers are changed. However, this might clutter the Rd and make it even longer than it is right now. Any thoughts?