Add support for DataDrivenDBInputFormat & Add a JDBCScheme builder.

[granthenke]

This is a rough port from Hadoop with the minimal amounts of changes needed. I also added a builder to JDBCScheme to help with the various forms of constructors. This can definitely be done more cleanly when moved to https://github.com/Cascading/cascading-jdbc.

See user group discussion: https://groups.google.com/forum/#!topic/cascading-user/HbJdrLKOLH8

[granthenke]

Below is a link to the sources from Hadoop:

http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/lib/db/

[granthenke]

This may also fix issue #18. I have done various tests and the performance was acceptable. In one test 1.5 trillion unique records were retrieved from a Teradata DB with 30 concurrent reads (and 30 reducers) in just over 4 hours. (Note: The number of concurrent reads and reducers may not be the most optimal.)

Explicit tests for Postgres may need to be done to be sure.

[johnynek]

we're moving this code here:
twitter/scalding#779

but JDBC is removed. We recommend cascading-jdbc now.