Where clause Validation

[tabdulradi]

Troy should be able to validate where clause.

Notes that where clause is common between Select, Update, and Delete. But with slightly different rules in each case.

There is already a placeholder for this code https://github.com/cassandra-scala/troy/pull/65/files#diff-b73eab8cad58acc28fa6a7152da0b27d https://github.com/cassandra-scala/troy/issues/36