add 3 methods: extend, clone and defaults
Add SchemaBuilder and SchemaPlugin for enable DSL modeling
Add Id SchemaPlugin for id type and id auto generating
Add CreatedOn SchemaPlugin for CreatedOn type and time auto generating
Add DomainBuilder for configuring two plugins to enable DSL modeling
update comments
Add DocuemntVersion schema plugin to define version key for optimistic locking
Add UpdatedOn schema plugin for createdOn auto generating and populating
Add CreatedBy schema plugin for createdBy auto populating
Add UpdatedBy schema plugin for updatedBy auto populating
Update comments
plug DocumentVersion, CreatedBy, UpdatedOn and UpdatedBy plugins
Add Thing model in replace of Deal in the future
Add mock and test for Thing model