Refine API to create and render CQL object specifications

[mp911de]

Right now, we have a series of entrypoints for CQL specification creation and generation such as AlterColumnSpecification.alterColumn(…) and AlterKeyspaceCqlGenerator.toCql(…). Each pair needs to be discovered independently and that is sometimes a challenge given the number of objects we have.

It would be great to have a Specifications.alterColumn(…) and CqlGenerator.toCql(…) variant to keep entry points together.