Rewrite of script

Rewritten from ground up to be a little more object oriented and easier
to maintain.

Also changed mapping so that a Redmine issue becomes an OmniFocus project,
which matches GTD guidelines better than mapping Redmine projects to
OmniFocus projects.

In Redmine, a project is generally thought of as a product with many activities
that are performed to create and improve it.  In GTD, this would be more of a
category.