couple clean ups for spawn

- uses tryLock(timeout) instead of if tryLock() else sleep(timeout)
- two cases of creating arrays to iterate over instead of just iterating
over the collection. toArray is implemented as an iterator call by
default anyway so I can't think of any reason for this
- collapsed a nested try statement
Move spawn background tasks to ThreadPoolExecutor.
[maven-release-plugin]prepare release v4.2.2
[maven-release-plugin]prepare for next development iteration
slightly less broken throttling hack
Implemented jdbc SpawnDataStore with postgres and mysql implementations. Modified DataStoreUtil to support automatic cutover on startup.
Removed unused h2 dependency.
Minor -- fix pom formatting.
Add timer metrics to jdbc data store.
Optional domain rewrites for gdrive export.
Send email notification for failed bkground events.
Fix to google drive authentication.
Switch to postgresql version available on maven central.
Javadoc documentation for TimeField class.
Add support for CSV arrays in RPN calculator.

This feature may be useful in combination with the merge operation
that appends keys together with a "," separator.
Replace if-chain with switch on String object.

Java 7 supports switch statements on Strings.
Addition of "vector" calculator operation.

The "vector" operation modifies the behavior of the next
operator to pop all elements on the stack and push a
single element onto the stack. "vector" is currently implemented
for addition, multiplication, min, and max operations. This
alleviates the need for N forms of vector operations.
Bugfix for BundleCalculator recent pull request.

Not all custom value types implement the asString() method.
This fix is a workaround for that fact.
add cross-domain query support (same as was added for spawn/minion)
minor - remove unused variable