[SPARK-4213][SQL][WIP] ParquetFilters - No support for LT, LTE, GT, GTE operators

Following description is quoted from JIRA:

When I issue a hql query against a HiveContext where my predicate uses a column of string type with one of LT, LTE, GT, or GTE operator, I get the following error:
scala.MatchError: StringType (of class org.apache.spark.sql.catalyst.types.StringType$)
Looking at the code in org.apache.spark.sql.parquet.ParquetFilters, StringType is absent from the corresponding functions for creating these filters.
To reproduce, in a Hive 0.13.1 shell, I created the following table (at a specified DB):

    create table sparkbug (
    id int,
    event string
    ) stored as parquet;

Insert some sample data:

    insert into table sparkbug select 1, '2011-06-18' from <some table> limit 1;
    insert into table sparkbug select 2, '2012-01-01' from <some table> limit 1;

Launch a spark shell and create a HiveContext to the metastore where the table above is located.

    import org.apache.spark.sql._
    import org.apache.spark.sql.SQLContext
    import org.apache.spark.sql.hive.HiveContext
    val hc = new HiveContext(sc)
    hc.setConf("spark.sql.shuffle.partitions", "10")
    hc.setConf("spark.sql.hive.convertMetastoreParquet", "true")
    hc.setConf("spark.sql.parquet.compression.codec", "snappy")
    import hc._
    hc.hql("select * from <db>.sparkbug where event >= '2011-12-01'")

A scala.MatchError will appear in the output.