Don't use finalizers to close cursors
Updated to current standard write concerns
No need to call getError on writeResult. any errors for writeConcern level will throw exceptions and be caught in catch block
Set default thread count to 100 when thread count is not specified
Added 'Install Maven and Java' instructions Ycsb config parameters
example
Add maven bash env vars
add instructions to install java via yum/apt-get
added support to specify readPreference
Update mongodb/README.md with more specific info

Changed reference to original forked repo which is not maintained to this repo to avoid conflicting instructions.   Might want to do that for top level README as well.
Revert to the central YCSB repository.
Change inserts to upserts in mongoclient

When running workloads that use the "insert" operation, we get a lot of
duplicate key exceptions from the server. Changing to upsert to avoid
these exceptions.