TACHYON-198 Move UserConf usage to use TachyonConf

This PR consist next steps to integrate new configuration work:
-) Remove usage of UserConf
-) Push TachyonConf to Tachyon Hadoop's file system (aka TFS class).
-) Remove UserConf.java from repo.
No its not. The hadoop case looks like this:

get FS
read conf
merge conf into FS

You can make it like the following:

read conf
get FS given conf

This makes it harder for users to do weird things with the API.