tools: move accounting tool from Documentation

Move accounting tool to tools and remove it from Documentation
Makefile. Update location information for this tool. Create a
new Makefile to build accounting. It can be built from top level
directory or from accounting directory:

Run make -C tools/accounting or cd tools/accounting; make

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>