Version 3.1.0 - fixes for focus issues; postpone to "next tuesday"

@mjdescy put in a lot of work to chase down and fix a lot of focus/task selection issues that became more prevalent in the 3.0 release. He also fixed some due date parsing issues and a priority sorting issue.

@Piscean added the ability to postpone to a named day rather than needing to know how many days away it is.

Thanks to you both for your work :-)