Add concept of staleness to the display based on the modification date

[austinlouden]

The goal of this feature is to give users an idea of which projects are becoming stale and should possibly be pruned.

• If a project has been worked on in the last week, then it's considered active and shown at the top.
• Projects that have not been worked on in the last week are considered stale, and shown in a separate section with a yellow header.
• Projects that haven't been worked on in the last two weeks are degrading, and should possibly be ended. (Shown with a red header).
• Projects that are at 100% are shown in a completed section.