Stop ignoring directories

[adamhathcock]

This was lazy/dumb of me to insist this. People get issues like this: https://github.com/Strachu/FileArchiver/issues/1

Look over where entries for directories are ignored. This was recently changed for 7Zip.

[adamhathcock]

Extraction looks okay. Need to see about actually creating archives with empty directories and creating empty directories in helper extensions.

[yoshiask]

Are there any new thoughts on this? My project relies heavily on both reading and creating archives with directories.

[adamhathcock]

PRs welcome. I'll approve this change to make empty directories