Add logging for N1QL queries
Add logging for N1QL queries

Motivations
-----------
When debugging applications, knowing the precise N1QL text used for a
query can be important.  There should be a method of logging this during
query execution.

Modifications
-------------
Added Debug level log using Common.Logging in BucketQueryExecutor.

Notes
-----
I gave some consideration to also logging errors during query execution.
However, these are currently logged by the Couchbase library, so logging
them again seemed redundant.

couchbaselabs/Linq2Couchbase,brantburnett/Linq2Couchbase,drGarbinsky/Linq2Couchbase