CDAP-693 Various small fixes to make sure it works on supported
Hadoop versions. Carry over the long overflow fix to the record
reader for hive, and change 'timestamp' column to 'ts' to avoid
reserved keyword problems on some versions of Hive. Also
classifying stream tables as tables that are backed by datasets
so that the UI will correctly mark those tables as CDAP tables.

Also adding classloader magic to get it to work on cdh4 as well
as more comments so we dont forget why certain things were done,
such as implementing the SerDe interface which is deprecated in
Hive13, but required for older versions of Hive.