swsh_samp null models can be used with non-integer quantities

swsh_samp, swsh_samp_c and swsh_samp_r null models shuffle original
cell values and can also be used with non-integer data. They were
unnecessarily restricted to integers. The swsh_both models
redistribute individuals among non-zero cells and can only be used
with integer values.
Avoid $ with data frame, and force asp=1 in plotting maps of points
Avoid some $ signs in adonis examples
Remove $ from clamtest example
Remove dollars from mrpp and multipart examples
Use residuals(x) instead of x$residuals in permatfull examples
ordisurf has formula & data=, it does not need with()
clean up edits
Further clarification of swsh methods, like suggested by Peter Solymos
Merge pull request #63 from jarioksa/swsh-samp-works-with-double

swsh_samp null models can be used with non-integer quantities
Merge pull request #65 from jarioksa/dollar-and-data-usage

Dollar and data usage