NCBC-278: Lock WebClient when getting WebRequest

WebClient is not thread safe

Change-Id: I92e6aa78d58a37ee41e02d516a836defc17efa6f
Reviewed-on: http://review.couchbase.org/27355
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Reviewed-by: Saakshi Manocha <saakshi.manocha@globallogic.com>
Tested-by: Saakshi Manocha <saakshi.manocha@globallogic.com>
Don't return response.OutputStream if response is null

Throw an 'InvalidOperationException' instead

Change-Id: If8830abc67849f61f60320f32c3c51ccf9e8fc6e
Reviewed-on: http://review.couchbase.org/27358
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Reviewed-by: Saakshi Manocha <saakshi.manocha@globallogic.com>
Tested-by: Saakshi Manocha <saakshi.manocha@globallogic.com>
MeepMeep, sample for worload generation.

Added simple sample that could be used to generate workloads against
Couchbase.

Change-Id: I79ad6cac7b4a6e83b89c3c587d5c98d5e32ffd82