Add functionality for DDL statements to add, drop and update cubes.

[amoghmargoor]

After adding support for Quark's DDL statement to Calcite in issue#34, we need to add corresponding functionality for cube, measure and dimensions to Quark.

[vrajat]

I want to see a design for this before getting into code.

[adeshr]

One way to do it, is to follow the same approach used in case of View:

1. New pojo for Dimension, Measure (Already have pojo for Cube).
2. Changes in dao's, mapper's, db.schemaFactory.
3. Changes in DDLPlanExecutor. (Here alter/create methods can be merged)