Ideas for search bar improvments

[tristanlatr]

• Give better ranking when an object matches multiple clauses, I think this is already done by lunr. But some queries will generate unexpected result ordering. Like ensure parsed will not yield ensure_parsed_docstring as the first result in the list.
• astutils. should list all members of the pydoctor.astutils module (translated to astutils.* *.astutils.* in lunr syntax) This has been addressed in Search bar improvments and Help page #823
• Add wildcard in between dots so users can use only the first letters of module names, liket.w.t.tag might be translated to t*.w*.t*.tag* *.t*.w*.t*.tag* in lunr syntax
• Change the default logic operator in between clauses: Currently all clauses are ORed together, so the number of results will increase every time users enter a new clause. Which is not a great user experience IMO. We could ANd the clauses by default and add a button to change the search logic.
• Another way of fixing the issue above is to ANd the clauses together if no clauses have an explicit presence, so foo bar would become +foo +bar and +foo bar would stay the same. As a side effect this will make impossible to define query with only optional terms.