first attempt at an RDD to pull data from JDBC sources
prevent mysql driver from pulling entire resultset into memory. explicitly close resultset and statement.
code cleanup per rxin comments
add test for JdbcRDD using embedded derby, per rxin suggestion
Merge branch 'jdbc' of github.com:koeninger/spark

Conflicts:
	project/SparkBuild.scala
Added derby dependency to Maven pom files for the JDBC Java test.
Added a comment in JdbcRDD for example usage.