tests/integration/script.py: Test element relative search paths in Element.search()

This adds some subprojects to the integration test, and extends the script
layout test such that it tests:

  * The original layout test

  * Addressing elements in subprojects

  * Addressing elements in subprojects when also loaded as a subproject
    (i.e. this test that searches are element relative, and not
    simply searches for full element paths).
15 files changed