HPCC-11348 ecltest setup missing some options

Add platform specific Setup result handling.
  It search the Setup related keyfile under ecl/setup/<platform>/
  directory first. If unsuccessful then it tries in ecl/key/.

Add parallel execution capability for Setup.

Update README.rst with these changes.

Add small changes to make coverage generation easier in Overnight Build
and Test System

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>
Merge pull request #5812 from AttilaVamos/HPCC-11348-fix

HPCC-11348 ecltest setup missing some options

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>