presenter.formatter.DateFormatter fixes

- PCTLIBRARY-1084: DateFormatter gets the timezone offset wrong if it contains half hours or quarter hours (@janh).
- PCTLIBRARY-1136 Bugfix: changed the if condition to check the date format to be an instance of Date (@jasonn).
PCTLIBRARY-1068: sub task 1112 Fix knockoutplugin bug which deals with 'click' events in verifier (@jasonn).
NO-JIRA: code style update with some changes to the actual code (checks for null, undefined, simplified if/else, ...) (@ewant).