Accept distribution versions of the openlayers library

Problem/Motivation

The openlayers library is also available in reduced fingerprint distribution archive. However directory structure is not the same thus js/css file pathes are not currently found by this module.

Steps to reproduce

1. Download and extract https://github.com/openlayers/openlayers/releases/download/v6.14.1/v6.14... in the openlayers3/versions directory.
2. Configure this version
3. Try it !

Proposed resolution

The attached patch enables the use of reduced distribution archives by checking the directory structure to determine the file locations.