[SETL-5] Implement Json Extract and Load

[furkanvarol]

Implemented JsonExtract which extracts JSON file(s) as org.apache.spark.sql.Rows, and JsonLoad which loads org.apache.spark.sql.Rows as JSON formatted file(s). Both mechanism assumes that each line (will) has and one JSON object.

[msimav]

JSON Extract is a compound operation consisted from file extract and then JSON transform and
JSON Load is a compoun operation too. What are the adventages of having those oprations as separate classes instead of just combining what we already have?

[furkanvarol]

You mean we should implement this functionality with what we already have or we should not have implement it at all?

[msimav]

I mean after #12 is merged we will have RowToJsonTransform and JsonToRowTransform classes which we can combine with FileExtract and FileLoad classes to achieve the behaviours of JsonExtract and JsonLoad classes.

[furkanvarol]

I see, okay I will change it after #12 merged.

[msimav]

Those primitive operations must be composable without creating new classes. This class is not only meaningless but also an antipattern that we must avoid as library authors.