Rollercoaster Tycoon 3 Object Importer Code

* FIX3: Fixed bug that caused scenery visual options to be wrongly written in some circumstances (reported for the no shadows flag).
* FIX3: Added 'None' to theme types. The set will be always visible, no matter which types are filtered (like in the cathegory changer).
* FIX3: Added Extra Parameters for pool items. Ramps don't seem to work and the Life Guard can currently not be done fully (requires two extra parameters, which the importer cannot do).
* FIX3: Replaced Unknowns 3-5 with Def.Color 1-3