Typedpy

This is a major update.
it adds support for static typing, which was a major ommission in the typedpy set of features. This means that developers now get intellisense and type checking in Pycharm or VSC.
This is achieved by automatic generation of python stub files (*.pyi). See more detail in the docs.

Main improvements:
Significant improvements in Structure API
- re-use of classes - Extend, Partial, All FieldsRequired, Pick : https://typedpy.readthedocs.io/en/latest/structures.html#alternative-methods-for-structure-reuse
- Abstract Structures: https://typedpy.readthedocs.io/en/latest/structures.html#abstract-structure
- Ensuring the fields in a structure include all enum values: https://typedpy.readthedocs.io/en/latest/structures.html#ensuring-field-names-include-all-possible-enum-values
- PEP-604 style of fields https://typedpy.readthedocs.io/en/latest/structures.html#support-for-pep-604-style
- Throw exception if class definition is wrong. For example: if the default value is mutable.

Serialization
- Update code-Schema mapping to be up-to-date with recent features and serialization mappers
- Support for "Constant" in serialization mappers
- HasTypes mixin for a base class with multiple types

Other
Many defect fixes and small improvements to API's.

Major improvements:
issue 99 - better support for python field types. See [documentation] (https://typedpy.readthedocs.io/en/latest/fields.html#combining-python-and-typedpy-types-in-field-definition)

Minor improvements:
issue 93 - In a Versioned structure, assign version based on the number of mappers in _versions_mapper

Defects:
issue 95 - deserializer with camel_case_convert option requires _additionalProperties
Issue 96 - Serializing Optional SerializableField does not invoke serialize()
Issue 97 - Error deserializing versioned structures
Issue 98 - AnyOf[NoneField, SerializableField] does not serialize correctly

91 defect: _required on inherited values does not work
92 defect: classreference must not be allowed to be passed as None

82 serialize field does not resolve field from a super class
83 support deserializer by a discriminator field
84 defaults should be assigned to the structure
85 annotation form does not work with "from future import __annotations__"
86 serialization mapper inheritance does not work correctly.
88 support aggregation of multiple mappers in a single class
89 Versions mapping
90 Support deserialization of older versions to latest

cleanup of code style issues.

Issue 69 allow bound method to be accepted as a value for field of type "Function"
Issue 70 allow to ignore assignment of None to a field. Useful when mapping from SQLAlchemy
Issue 71 Optional parameter to serializer/deserializer to convert between snake-case field names and camelCase. Useful when mapping between python names and names in Java/ Javascript, which use camelCase names
Issue 72 Fix a bug in Structure.fields_by_name() when using the syntax of field annotations.
Issue 73 clone a structure with overrides. Useful especially when you have an immutable structure, and you want to create another instance that is similar, but not identical.
Issue 74 expose mapping from exception String to a well formed structure for error info. Useful when the calling service/function needs a consistent way of handling errors
Issue 75 add option to output all errors when initializing, instead of failing on first error
Issue 76 fix error formating
issue 77 make decimal serializable
Issue 79 make __repr__ behave like __str__
Issue 81 explicit cast