Added java async tests that open many connections.  refs #1332.
Changed async test retres after EBUSY to use exponentially longer retries,
to guarantee successful runs.
Add typemaps so Java close cleanups occur after 'close' completes. refs #1332.
Some refactoring and simplification of close code.
KNF whitespace.
Merge pull request #1357 from wiredtiger/java-async-close

Java async close