Recalculate resource refs on editor update

[olensmar]

We currently recalculate resource refs when a resource is saved in the source or form editors - we should be able to recalculate while the user is editing - given that we:

• use a debounce to avoid recalculating for every keypress
• only recalculate links that could actually be affected by changes in the current resource
• update the underlying resource and mark it as "dirty" somehow - also in the navigator - so that users can save it later or do batch saves (as suggested by Batch-save of changed resources #180