reset the PluginManager (as this shouldn't really need to be done). Cleaned up all unit tests so they follow the same structure and
uses this base class where necessary and eliminates a lot of duplicate code.
Updated DynamicPublishedContent's methods to just proxy calls to the new extension methods so that all of the logic is contained in one place.
Added new GetRootDocuments to the IPublishedContentStore since we need this in order to get the root list of documents for many of these methods.
Fixed an issue with the DynamicNode to IPublishedContent converter.
Fixed many of the failing unit tests.
