Write incoming processor script in Hy and improve

Rewrote the incoming processor Python script in Hy-lang.

When considering incoming assets to process, ignore directories that are
less than one hour old. A new command-line argument bypasses this check.

When splitting a directory name by underscore, ignore any empty elements
(i.e. the directory name had a double underscore).

Send an email report of the assets that were processed, organized by
tags. If the email send fails, dumps to standard output. Defaults to
sending to root@localhost.