Issue #454 ColumnFamilyIterator

[bharatendra]

Added ColumnFamilyIterator and a test case for the same.

[bharatendra]

I Updated the ColumnFamilyIterator to use ColumnSliceIterator and KeyIterator internally. Now the code is much simpler.

I noticed that I can not instantiate the ColumnSliceIterator using null value for finish parameter. For ex:
new ColumnSliceIterator(sliceQuery, null, null, false, maxColumnsCount). It is throwing NP exception.
I need to specify
N finish = null and use new ColumnSliceIterator(sliceQuery, null, finish, false, maxColumnsCount)

The key iterator may not return keys if all the columns are deleted in a row. May be it is useful to allow option to set keysonly to use setReturnKeysOnly() internally

Also the ColumnSliceIterator;:hasNext() can throw NP exception if column family has on columns or a row contains no columns. I will test this and update you later.

[dserdyuk]

Any information on which release is going to include these changes ?
thanks in advance.