fix handling of analyses list

Previously, if a parent data item was closed, its child analyses
were not removed from our analyses list.  This could cause a bus
error if we later attempted to save the current workflow.

Now, when we close a data item, we recursively check all child
items to see if they are analyses, and if so, they are removed
from our list.
update Ok button on load from mongo dialog

If we connect to a new mongo database, or reconnect to the same one,
disable the "Ok" button if no workflows are available for loading.
Previously, once the Ok button was enabled, it remained enabled.
Merge branch 'minor_mongo_fixes'

* minor_mongo_fixes:
  update Ok button on load from mongo dialog
  fix handling of analyses list