CMake: Add support for framework tests

Created by: girishpathak

This change adds CMake build and execute support for framework tests.

Also updated is the doc/cmake_readme.md with instructions for building and executing framework tests.

Change-Id: I460398e26c427cd6af8da298c054377175c91d1c Signed-off-by: Girish Pathak girish.pathak@arm.com