For #25555 - Framework & engine blocks can now be included in envs
This is consistent with the existing support for apps.
For #25582 - Resolved recursive trap in frameworks install.
If an APP required frameworks A and B and framework A also required framework B and none of the frameworks had been installed, an exception would be raised because of the depth-first manner the recursion was carried out. Changed to breath-first to that the environment object is correctly representing the changes that are carried out as part of the recursion.
For #25555 - Added error message for referenced framework install.
This is similar to the message which is already current generated if apps or engines are installed into referenced sections.
Closes #77