Export filtered IFC files

Currently, the IFC export function exports ALL data from a Named iModel Version and this results in very large and messy IFC models that are not appropriate to be used for client submissions.

The ability to create filtered IFC files would allow the IFC export function to be much more practical and usable as part of model exchange with clients. This could be implemented by only exporting elements displayed in selected Saved Views or the ability to select what elements to export using the model tree, etc.