Add dropdown item "Download Data as XLSX"

It's currently possible to download Data as CSV and TSV formats.

Please add dropdown item "Download Data as XLSX".

XLSX format has following advantages over CSV/TSV:

• it can carry also data types not just data;
• it can have compression built in;
• there is no csv import wizard to run - xlsx is self-descriptive.

XLSX format has several advantages over XLS:

• limits are 1,048,576 rows (vs 65,536 in xls);
• 16,384 columns (vs 256 in xls);
• main advantage is XLS is a proprietary binary format while XLSX is based on Office Open XML format.

Cloudera's Hue for example does allow do download query results as xlsx and our analysts find it very useful.