Adding traits::WrapperBase to identify wrapped classes

relates #129
Merge branch 'issue_46' into develop

Accidentally did this on another branch, relates #129
Rename WrapperBase to ElideMinimal

Removed WrapperBase and added ElideMinimal instead, which is a trait that is checked by
text archives performing minimal serialization to see if they should go ahead and skip creating various nodes
and naming things.  Currently only used on base_class and virtual_base_class