Add the lastModificationTimeMs into Inode

Add the lastModificationTimeMs into Inode. Update the Inode, InodeFile, InodeFolder.
In order to see the modification time on WebUI, update the WebUI.
The Inode's lastModificationTimeMs will be set whenever the Inode's metadata changes.
why call System.currentTimeMillis() here instead of in the mMasterInfo? Since other calls like create, delete all called inside of mMasterInfo