Adminotech Tundra 2.4.1 fixes

* Fix AssetInterestPlugin (optional plugin) to build with the new TundraCore. This is not afaik in the default build so was overlooked when porting to the new TundraCore.
* Remove obsolete signal connection in EC_SlideShow now that the new attribute change detection is used.
* Fix EC_Highlight to restore EC_Mesh materials when its hidden or removed.
* Fix EC_Mesh bugs caused by the changed behavior of SetMaterial. The situations were failed material requests, setting empty refs no reset "base" material and pending material tracking that I removed as its no longer needed. Added pending failed material tracking until mesh is loaded as we want to show the visual error material in all situations.
* Fix cmake INSTALL project build by removing non existing file copies (the OpenAL likes should be also removed, there is no oal_wrap.dll anymore).
* Fix cmake INSTALL project to correctly copy TundraCore.dll into the target path root not to /plugins.