Implement warning to users about storage limit

[Dan Bean]

PHP call to manager.php on page load to determine remaining storage. Add to home.php builder.php

Gentle warning if approaching limit, big warning if limit reached. Disable save online and save a copy on all pages for this user, replace the text with something relevant to the storage limit.

[Dan Bean]

Fix issue #19 - warning about storage limit. Upload in the Diagrams tool is experimental in this version.

→ <<cset 751b338192f6>>