HACKING.rst: Add running a single test example

See merge request !597

A project path is a path relative to a project directory.

A project path can not also refer to the parent directory in the first
path component, or point to symbolic links, fifos, sockets and
block/character devices.

The autotools example had to be copied over inside of the junction
example, as referring to a path outside of the project directory is
now disallowed.

Add validation for project paths

See merge request !593

This is required to be able to build a Loader before the list
of targets is known.

Fixes #331.

Add support for include in project.conf

Closes #331

See merge request !471