Removing validation on the FirstName and LastName properties from the RegisterModel ViewModel.

There are more name possibilities than someone can hope to write a regular expression for: http://stackoverflow.com/a/888868/383710
Fix Issue #189

Changed the overlapping date logic to handle cases where the start and end date span over and existing commitment.
Added tests to cover all aspects of date comparison for existing commitments.
Merge pull request #204 from xdaDaveShaw/master

Fix Issue #184