Support more complex file name patterns/regexes
We currently have the `meta/file-extension` attribute for specifying which file extensions a format uses (when data in the format is stored as a file). This is sufficient for most file formats, because file extensions are an established standard nowadays. However, some file formats have different naming schemes, which currently cannot be specified in a KSY spec:

* Fixed names with no variable parts, for example Windows "Thumbs.db" and Mac ".DS_Store".
* File extensions that follow a known pattern, but there are too many to list explicitly, for example split RAR files ("filename.r01", "filename.r02", "filename.r03", ...) and compressed DOS/Windows installation files ("filename.ex_", "filename.co_", "filename.sy_", "filename.tx_").
* File names that follow a known pattern, but don't have a (relevant) file extension, for example AppleDouble files ("._filename") and CVS version history files ("filename,v").

To specify these naming schemes in KSY, a more powerful mechanism than the current `meta/file-extension` is needed. This would be a new attribute that allows specifying the entire file name using some kind of pattern, rather than just the extension using fixed strings.

Options for the pattern language include regular expressions and shell-style glob patterns. Glob patterns are simpler to understand and write, whereas regexes are much more powerful. I think glob patterns would work better, because people are already used to them for specifying file name patterns in the shell, and the complexity of regexes is usually not needed for file names. For example, `*.r??` is clearer than `.*\.r..`. Also note that `.` is a wildcard in regexes, which is confusing to read in combination with literal dots that appear in file names.

Another question is whether the `meta/file-extension` attribute should be deprecated/removed when this new attribute is added. If we decide on regex-based patterns, I would definitely keep the `file-extension` attribute, because for the common case of a simple file extension it's sufficient and easier to read (`zip` vs. `.*\.zip`). If we decide on glob patterns, we could consider removing `file-extension`, because it's not much more complex in comparison (`zip` vs. `*.zip`).