Hidden files

[battis]

bdcd13be5a2b6057ccf7c8d1ae8e01c770134313 introduced hidden files in the index which required manual editing of index.json There needs to be a way to make this more easily configurable. And being able to differentiate between "hidden in directory listing" and "hidden from search results".

Probably one of two paths forward. Either:

1. Include a very few hidden files in config.json (easiest?)
2. Add a dot file in a directory to add arbitary information to index file (e.g. .index at root of directory is an array something like:

   [
   {"id": "<google drive id>", "index": {"hidden": true}},
   {"name": "<file name>", "index": {"hidden": true}},
   {"id": "<google drive id>", "name": "Replacement file name"}
   ]