db:data:dump_dir produces malformed directory names on Windows

[ccarlson71]

The inclusion of the time produces invalid directory names due to the colons.

Changing line 27 of yaml_db_tasks.rake to:

dir = ENV['dir'] || "#{Time.now.to_s.gsub(/ /, '_').gsub(/\:/,"-")}"

fixes the problem, replacing colons with dashes.