Release issues of DATAVIEW 2.3

[ChangxinBai]

0: Never release any confidential informations, such as amazon account, dropbox account and database account.
1: Code refactoring: Where should these files belong? CmdLineDriver.java, MSGClient.java, MakeMachinesReady.java, MoveDataToCloud.java, MoveToCloud.java. -- ongoing work
2: Abstract classes for VMProvisioner and TaskExecutor:
What common methods should we have for VMProvisioner.java and
TaskExecutor.java? Maybe we can define an abstract VMProvisioner.java
and TaskExecutor.java and allow different developers to develop their own VMProvisioner and TaskExecutor. -- ongoing work
3: Use pure image as the default template and send taskExecutor to each instance to avoid image losing.