Move some codes from AnnotateModels to AnnotateModels::SchemaInfo

[nard-tech]

See also #794

AnnotateModels is fat and so hard to maintain.

In order to reduce code lines of AnnotateModels, I moved constants and methods defined in AnnotateModels to another namespace AnnotateModels::SchemaInfo.

AnnotateModels.get_schema_info is moved AnnotateModels::SchemaInfo.generate. Other methods are not renamed.