Do not load defaults with configuration

The fix includes the following changes : 

* Grill session config and query config load no more defaults (No defaults loaded from core-default.xml, core-site.xml, hive-default.xml and hive-site.xml).
* Separated grill-default.xml into  grillserver-default.xml and grillsession-default.xml. Session config will only load the grillsession-default.xml and server would only load grillserver-default.xml. Both server and session defaults can be overridden in grill-site.xml on the server.
* Server still loads the defaults (core-default.xml, core-site.xml, hive-site.xml) config sothat hadoop and hive configurations can be picked by server. 
* Fixes grill client not to load any default configurations.
* HiveDriver loads configuration from hivedriver-site.xml.
* Fixes setting query configuration upon server restart.
* Moved all restart tests into separate class to run them after all unit tests. It was easy debug restart tests as well.