Further clarification of in-place on Windows. (rebased onto develop)


This is the same as gh-901 but rebased onto develop.

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This PR explicitly enumerates what in-place functionality is and isn't available under Windows. It aims to fix the issue discovered by @manics (5.0.3 testing spreadsheet, row 29).
Care will have to be taken when rebasing, as the ``.. note`` element won't be present on ``develop``.

To test: please make sure if the limitations are clear enough.

\cc @manics, @joshmoore, @pwalczysko, @mtbc, @rleigh-dundee, @sbesson