Improve feedback and error checking when decoding filters on first load

[KCMertens]

Currently the Lucene query AST is barely used when decoding filters, instead the query is heavily simplified.
Usually that is fine, as it only has an effect when the filter query is different from what is in the UI.
But it can create issues when the filter query is generated by an external source (another app linking into the Corpus-Frontend) and that filter doesn't 100% correspond to what we expect given the configured filter widgets.

So,
Ideally, check whether the AST makes sense for the filter we're decoding, and print a warning if it doesn't.
As an extra nice-to-have, similar to the pattern query, have a bailout that just plops the filter in a textbox somewhere if decoding fails?