uninstall: show etc/var files from poured bottle

[cho-m]

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This avoids outputting rm -rf messages for poorly guessed files which some users blindly run and then lead to breaking other formulae.

One demerit is this no longer guesses generated configuration files.

For source installs, keep the guesses but add more warnings to try to prevent users from removing files without confirming them.

[MikeMcQuaid]

Makes sense to me, good idea!