Empty tags content if not used

I would take benefits of an option that would reset the tags content, before any state change.

For example, I use open-graph meta in few states on my application. I expect them to be empty in other states ; by now to make it work I must add

in any state.

Start by tracing how AngularJS state changes trigger meta-tag updates and where tags absent from the new state are handled. Verify the behavior with the existing application or tests, if available; done means unused tags are cleared automatically so each state does not need an empty update-meta element.

Written by the indexing model from the issue text.