Moved type mapping classes from Relational.Model to Relational and removed the Relational.Model namespace.
Updated code to gnerate CSharp code for AddForeignKey that is formatted on multiple lines.
Removed MigrationAssembly and MigrationNamespace from RelationalOptionsExtension.
Added a MigrationsOptionsExtensions instead.
Added MigrationsDbContextOptionsExtensions with the methods UseMigrationAssembly, UseMigrationNamespace.
Updated related code and unit tests, added a couple new unit tests.