Search Extensions: support custom note title

The problem

When a plugin creates a note with search results, it uses search terms as the note title.

Now, if afterwards I rename the note (to be more descriptive) and then click "refresh" link in the note, it creates a new note with fresh search results instead of updating the existing one (obviously, because it is looking for a note with a corresponding name).

Proposed solution

Allow user to optionally specify custom note title when he or she is performing the search (new input in the UI of /flexiSearch would be absolutely enough for me personally, although some other users who use the plugin commands without the UI might want an optional parameter support as well).

This way one still won't be able to change the note title after search results note has been created, but at least one would be able to set the title before creating that note.

Start at the /flexiSearch UI and trace how search results notes are created and later refreshed. Check whether the plugin command path is separate, then verify that an optional custom title is preserved so refreshing updates the existing note instead of creating a new one.