Auto-deserialization of base templates + small fix for standard fields

Added auto-deserialization of base templates (previously, only the first item template that was encountered was deserialized) and a fix for handling standard shared fields during deserialization.

Also, it turned out that the 'field copying' done in the template deserialization pipeline was redundant; the pipeline for deserializing regular items is also executed. So I removed those processors.

Thanks for adding the readme stuff and getting it to work with NuGet, btw!