Major refactoring of the Cast API

Added capability of cast pipelines to provide positive and negative samples

Cast API passes the tests including the pipeline self-test

Tested features: fluent syntax, pipeline result types, positive and negative pipeline samples

Temporary comments removed from the builtins using Cast API

More comments removed

Some modifications of CastAPI following the review

Compilation warnings resolved

CastAPI names and FindFirst logic refactored

Cast API refactored and simplified

A little refactoring, EncodeString builtin using Cast API

A couple of "argument-heavy" builtins such as Scan adapted to the Cast API and some fine tuning of the API.

Using "and" filter operator in NGetText, the "missingValue" filter added, the MissingValue type handled in CastVectorNode

Null samples fixed

Checked the style

the scalarStringValue step added, the notNA steps copied to the initial phase