SES-1787 : Use failsafe plugin for integration tests

Now to both skip tests and integration tests you can use:

    mvn clean install -DskipTests -DskipITs
SES-1787 : Convert tests to use different port numbers so they can run
in parallel
SES-1789 : Support servlet attributes for setting data directory to
avoid using JVM system-wide property
SES-1789 : Use Jetty setAttribute to setup data directory
SES-1789 : Increase separation between tests
SES-1789 : Add PersistentMemoryStoreConnectionTest to work through the
possible causes of the threading bug that is being revealed by failsafe
plugin when it is run with parallel options
SES-1789 : Cleanup PersistentMemoryStoreTest to use JUnit
TemporaryFolder
SES-1789 : More work to get tests working in parallel