ClusterOptions need to support sasl_mech_force

The workaround is putting it in the connection string, like the certpath, but this really should be in the options.  

Also, check to see if we need to expose this in the bindings to be set by lcb_cntl.  I think probably not – this is only really a connection-time setting I believe, but look at that just to be sure.

Additionally, I'd bet there are other options we could support in there as well.  Lets examine the current set of supported options, find and support (or at least make issues for) any others that stand out.