Timestamp and Date classes which work in the catalyst DSL.

These Timestamp and Date classes support the usual comparison operators, so the can be used in catalyst Expressions.  The come with implicit conversions to and from the underlying Java classes.  They also have a convenient initializer which accepts a String.

Additional implicit conversions fix an issue with the DSL where expressions like 0 < 'x are not recognized.

An independent change adds a method to Row for creating a row from a sequence of Strings and a schema.
Yes.  Well, the truth is that I was originally working with the source for Spark 1.1.0.  When I pulled the current code it turned out that many lines such as this one had already been added after the release of 1.1.0, so I had to go through and remove many duplicates.  In the course of that process it seemed better for me to have some logical scheme to guide me in choosing which of the two duplicates to delete.