deletes some of the deprectated threading code since they are deprecated since 0.4
* deleted:    core/src/main/java/brooklyn/util/task/SingleThreadedExecution.groovy
* deleted:    core/src/test/java/brooklyn/util/task/SynchronizedExecutionTest.groovy
Merge pull request #739 from pveentjer/deleteDeprecatedBrooklynUtilTask

deletes some of the deprectated threading code since they are deprecated...