protobuf-net 2.0.0.621

* 2.0.0.621 - fix: nasty regression in r619, where GetSchema() could cause base-type corruption * 2.0.0.619 - fix: GetSchema() should use ultimate base-type names when modelling inheritance - fix: ensure precomile always generates a .ctor() on the concrete serializer - add: support out-of-order fields when deseiralizing inheritance from other protobuf implementations * 2.0.0.614 - fix: enum handling of ": byte" confusing signed/unsigned bytes * 2.0.0.612 - fix: allow adding enum maps at runtime via MetaType * 2.0.0.611 - fix: *Specified should work with non-public methods - performance: pre-compiled serializers now use dictionary lookups where appropriate - fix: nuget package for portable library should be more inclusive * 2.0.0.602 - added precompiler support for internal-types and [InternalsVisibleTo(...)]-forwarding - made AllowParseableTypes available on default type-model * 2.0.0.601 - added phone8 support