stress: optimize and add sync/async options

* use one generator per worker
* run async workers on a threadpool, don't block
Support null values in the query build

JAVA-105 #fixes
Add SSL support
Log a warning when schema agreement cannot be reached in 10 seconds
Ensure we don't overflow in ExponentialReconnectionPolicy

JAVA-107 #fixes
Make pom work on recent maven
Fixed StringBuilder and() method so that as CQL is readable

.append("AND ") to .append(" AND ") (Line 379)
Add support for unlogged batch in the query builder

JAVA-113 #fixes
Merge pull request #100 from mholland231/master

Fixed issue: Unformatted TableMetada.asCQLQuery() appends options.* without spacing
Minor typo