Formatter: add dump_format_ns to base Formatter class

`dump_format_ns` is a generic formatter to dump a simple format along
with a namespace.

Signed-off-by: Abhishek Lekshmanan <abhishek.lekshmanan@ril.com>
Formatter: extending xml_formatter with dump_format_ns

In lines of dump_format, allow an optional namespace argument so that
xml snippets with namespaces also can be accomodated

Signed-off-by: Abhishek Lekshmanan <abhishek.lekshmanan@ril.com>
Formatter: Extend JSON Formatter with dump_format_ns

This commit implements json formatter class with dump_format_ns which
generically dumps a namespace with json

Signed-off-by: Abhishek Lekshmanan <abhishek.lekshmanan@ril.com>
rgw_formats: stub a dump_format_ns

This commit adds a dummy dump_format_ns for RGWFormatter_Plain. The
method is not implemented, just raises a not impelemented error

Signed-off-by: Abhishek Lekshmanan <abhishek.lekshmanan@ril.com>
s3: update get_location based on new formatter

This updates the s3's get bucket location based on the new formatter
which allows xml ns to be embedded.

Signed-off-by: Abhishek Lekshmanan <abhishek.lekshmanan@ril.com>