Import: default ignore pattern to broad

I attempted to import a folder containing the albums "…Hits" and "...But Seriously" (notice that Hits has U+2026, but the other album only three dots). Because of http://beets.readthedocs.io/en/v1.3.17/reference/config.html#ignore, beets will _silently_ ignore the "But Seriously" folder.
(This probably not only applies to folders, but also to filenames: If someone previously tagged their files "$album - $track - $title", which I don't, but I imagine there might be people who do).

I consider this to be a significant problem; in a larger import, I would likely have missed this, and probably deleted the original folder at some point. So, it would be nice to sophisticate the default ignore patterns, and make beets more verbose about ignoring folders (at least when they contain files that could be audio).

There are more problematic cases, though. See

http://musicbrainz.org/release-group/eb13b70f-02f8-3c89-a4a9-0418252b0fdf

So just changing the pattern to `.[!.]*` is not really _the_ solution, either.

If someone had a good idea on how to improve the behaviour here, I'd really appreciate it.