CCTray Column Sorting Improvements

* Always start with ascending sort order when switching columns.
* Use natural sort order for text, thereby removing the need to sort
  integers differently, and handle project names with numbers correctly.
* Use a secondary (always ascending) sort on the first column for list
  items with the same cell content in the (higher) sort column.
Merge pull request #195 from mghie/master

CCTray Column Sorting Improvements