XD-1106: JDBC to HDFS module
XD-1106: Allow use of 'sql' option.

This allows more flexibility than just setting the table and columns.
Also renamed 'names' module to 'columns' for consistency with JDBC sink.
XD-1106: Read column names from result set metadata

The names are cached in the RowMapper on first use and used to create
the tuple.
XD-1106: Use Spring's JdbcUtils for reading result set
XD-1106: Fix regex group in AbstractHdfsItemWriter
XD-1106: Reset item writers initialization flag when item writer closes