Allow ColumnFamilyQuery#setConsistencyLevel to carry over to CqlQuery instances which it constructs.

Currently the following example code:

```java
final ColumnFamily<SomeKey, SomeValue> cf = getColumnFamily();
final String cql = getCql();
final CqlQuery<SomeKey, SomeValue> cqlQuery = getKeyspace().prepareQuery(cf)
    .setConsistencyLevel(ConsistencyLevel.CL_QUORUM).withCql(cql);
```

Will result in a CqlQuery that has the ConsistencyLevel still set to CL_ONE (the default in AbstractThriftCqlQuery). This pull-request fixes that by carrying over the CL from the ThriftColumnFamilyQueryImpl instance it is created with.