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.
I used the eclipse formatter: https://github.com/amplab/tachyon/blob/master/docs/resources/tachyon-code-formatter-eclipse.xml
And it's like that :)