propellor spin

(cherry picked from commit 1d02d589c79781cc4b0bd82467edbdf64c40f34d)
finished accidentially committed bit
changelog
another place to use toResult
refactor
Include Propellor.Property.OS, which was accidentially left out of the cabal file in the last release.
prep release
fix a case where fileProperty reported a change despite not making one

The problem occurred because two lists of lines of the file can be
different, while representing the same file content. For example:
["foo", "bar"]
["foo\nbar"]
Fix Apache.siteEnabled to update the config file and reload apache when configuration has changed.