MB-7102: Export to csv file if specified
MB-7102: Export to csv file if specified

By default, csv output to stdout. But if .csv file is specified,
it is desirable to export to specified file.
Uppper level directories will be created if nonexist

Change-Id: Ie7159d93908a642a578ac71c5dffd158b31ebb15

couchbaselabs/couchbase-cli,couchbase/couchbase-cli,couchbaselabs/couchbase-cli,couchbase/couchbase-cli,couchbaselabs/couchbase-cli