Include hive-default.xml and hive-log4j.properties in hive-common JAR

hive-common-*.jar should include hive-default.xml and hive-log4j.properties,
and similarly hive-exec-*.jar should include hive-exec-log4j.properties. The
hive-default.xml file that currently sits in the conf/ directory should be removed.

Motivations for this change:

• We explicitly tell users that they should never modify hive-default.xml yet give them the opportunity to do so by placing the file in the conf dir.
• Many users are familiar with the Hadoop configuration mechanism that does not require *-default.xml files to be present in the HADOOP_CONF_DIR, and assume that the same is true for HIVE_CONF_DIR.