HBASE-12493 Make User and TokenUtil public

Conflicts:
	hbase-common/src/main/java/org/apache/hadoop/hbase/security/User.java
	hbase-server/src/main/java/org/apache/hadoop/hbase/mapred/TableMapReduceUtil.java
	hbase-server/src/main/java/org/apache/hadoop/hbase/mapreduce/TableMapReduceUtil.java
	hbase-server/src/main/java/org/apache/hadoop/hbase/security/token/TokenUtil.java
	hbase-server/src/test/java/org/apache/hadoop/hbase/security/token/TestTokenAuthentication.java