Pyrin

* Added all common column helpers.
such as:
GUIDColumn, SequenceColumn, IntegerColumn, BigIntegerColumn, SmallIntegerColumn,
DateTimeColumn, DateColumn, TimeColumn, TimeStampColumn, FloatColumn, DecimalColumn,
BooleanColumn, TextColumn.

* Code revision
* Added SequenceColumn

* Important bug fix in sequence pk column
* Enhanced prefetching columns with default values

* Add unique_on attribute in model mixins

* Add auto validators
* Integrate columns with validators
* Improved validators structure
* Add dict and decimal validators
* Enhance model mixin classes
* Minor bug fixes
* Code enhancements

* Enhanced string normalizers to handle None values more customizable
* Extended History mixin entities