timer is started. If timer finishes before another change takes place,
project structure will be updated to reflect any changes in reference
comments or import statements.
changes in last s seconds (where s is currently 1.5), then check project
structure to account for references that may have changed. Turned this
off pending fix for getScriptFileNames returning only the root names.
Added event handler for deleted file, so that session can update error
messages upon deletion of a file from a project.
