1) remove some dead code from WinNtBusDriver.c

1) remove some dead code from WinNtBusDriver.c
2) change PCD_INVALID_TOKEN_NUMBER to 0 as stipulated in MWG spec and PCD spec.
3) support returning a Default Value when a read failure by variable service for PCD entry with Variable Enabled.
4) Remove a lot of unreferenced JAVA import from CollectPCDAction.java, PCDAutoGenAction.java, MemoryDatabaseManager.java, Token.java and UsageInstance.java.
5) Opimized to merge elements in all tables in PCD database for make the code compact.
6) Did a tighter check on how dynamic PCD entry is referenced in each module.
7) Update the PCD driver/PEIM and PCD database generation verion to 2.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@605 6f19259b-4bc3-4df7-8a09-765794883524