HPCC-7875 Enhance OUTPUT documentation to hint that 'format' does a project

Signed-off-by: Richard Taylor <richard.taylor@lexisnexis.com>
Merge pull request #4303 from RichardTaylorHPCC/B7875

HPCC-7875 Enhance OUTPUT documentation to hint that 'format' does a project

Reviewed-By: Richard Chapman <rchapman@hpccsystem.com>