doc: document python build scripts

We have a collection of python scripts that are part of our build
system.  This PR collects docstring comments added to these scripts into
a summary document.  Previous references to just the script name in
other documentation are updated to point to this build tool
documentation.

Some of the scripts needed an update to be processed (via include
directives) consistently.

Signed-off-by: David B. Kinder <david.b.kinder@intel.com>
Signed-off-by: Anas Nashif <anas.nashif@intel.com>