enable virtual core at java and bridge
format and comments change for CR
update for code review feedback
rename DefaultCore to DefaultNumberOfCores
update driver.dll
Merge branch 'master' of https://github.com/Microsoft-CISL/REEF into juwang-virtualcore
update tests
update after sync from .Net version
updated based on review comments
Merge branch 'master' into juwang-virtualcore
adding more logs about number of cores
Merge pull request #1002 from Microsoft-CISL/juwang-virtualcore

juwang-enable virtual core in Java Reef and clr bridge