Create indices according to specs

This PR creates indices [according to the specs defined in the wiki] (https://github.com/geoadmin/service-sphinxsearch/wiki/Search-Requirements)

- Remove all unnecessary stuff
-- Remove quadindex where it's not needed (swisssearch)
-- Remove detail where it's not needed (feature search for queryable layers)

- Use prefix for quadindex instead of infix (feature search for both queryable and searchable layers)
- Use infix of length 2 for all searches with detail search

- Make sure that all feature searches contain the same attributes

- Some refactoring to have clearer code

These changes result in [smaller indices and faster index creationg](https://github.com/geoadmin/service-sphinxsearch/wiki/Infix,-Prefix,-Star-Search)

Note that the current indices on the dev machine are created with this.