The location of composer’s vendor/autoload_real.php file is a good
indicator of the root of a project, and can be used to derive a
BASE_PATH
This gives us more flexibility about where the framework module is
installed relative to a project root. It also lets us use the framework
module as a project root, e.g. in test runs.
THIRDPARTY_PATH and ADMIN_PATH are calculated relative to this, and
the FRAMEWORK_DIR, THIRDPARTY_DIR, and ADMIN_DIR are relative to the
BASE_PATH.
The 'admin' module will be split off from 'framework',
where 'framework' only provides (mostly) frontend-agnostic PHP classes.
For example, HTMLEditorField.php has a TinyMCEConfig.php driver,
but doesn't come with its own JS includes.
