DNN-6132 Added code to make the conversion from null strings to integer just return the NullInteger.
Merge pull request #205 from donker/DNN-6132

DNN-6132 DNNEditList control logs error if no previous value was present
DNN-5965 Upgrade the 51Degrees library
Revert "DNN-5965 Upgrade the 51Degrees library"

This reverts commit de68a3937ce72bf83f9304fa5b1b419f535fb517.
DNN-6100 PortalSettings Refactoring
Renamed internal methods to make it more clear what the code was doing.  Also refactored constructors to eliminate redundant code.
DNN-6100 - minor resharper suggested code cleanup
DNN-6100 - Reformat file to make code more readable