Move Application Platform Override Manager into Application directory.
Add comments in Network library class to say they are only intended to be used by UEFI network stack modules.
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@7641 6f19259b-4bc3-4df7-8a09-765794883524
1. Add one OverrideVariableGuid in MdeModulePkg
2. Add one library PlatDriOverLib used by PlatformDriOverrideDxe.
3. Add PlatformDriOverrideDxe in MdeModulePkg
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@4557 6f19259b-4bc3-4df7-8a09-765794883524