Merge pull request #246 from Piscean/dev

Minor Help and Postpone fixes
Closes Issue #247: Changing filters causes loss of selection in task list.
Closes Issue #249: Bug: When there are duplicate tasks and one is selected, all get selected after sorting the task list.
Closes Issue #248: Bug: After editing a task, focus is not moved to the newly created or edited task.
This patch fixes a regression introduced in commit 645f572 (When duplicate tasks are selected, only one of those tasks retains selection after a sort, filter, or other operation). Closes Issue #249.
Closes Issue #250: Bug: When reloading the todo.txt file, task list selections are lost.
Closes Issue #252: Bug: After updating Options, task list selection is lost. Ensures that, after Options are set, the task list is refreshed only if options related to its display are changed. Those options are: "Current Font" (any font attributes), "Allow grouping of tasks", and "Filter text is case-sensitive".
Closes Issue #251: Bug: Pressing the Esc key in the text box causes focus to move to menus, etc.
Closes Issue #225: Bug: Priority (Z) sorts below No Priority (n/a).
Merge pull request #255 from Piscean/dev

Fix for Postpone to Tuesday bug where "Tuesday" didn't equal "tuesday".
Merge remote-tracking branch 'upstream/dev' into dev

Conflicts:
	Client/MainWindowViewModel.cs
Adding original version from Ben's director