Feature parity with OJS Plugin

[nuest]

Visit the issue descriptions in the "sister" plugin for OJS, and check which commit messages linked in the issue comments are related to the implementation. These commits should provide as starting point to implement the following features in Janeway:

• Add full screen option to map TIBHannover/geoMetadata#61
• Add setting to include GeoJSON download button gin side bar or not TIBHannover/geoMetadata#55
• Add ICBM address and geo.position to HTML meta tag TIBHannover/geoMetadata#87
• Add geo.region meta tag TIBHannover/geoMetadata#88
• Show overall period of time frames for an issue TIBHannover/geoMetadata#105
• Authors can add multiple time periods for an article TIBHannover/geoMetadata#57
• Map feature colours, including highlight on issue page, are configurable in settings TIBHannover/geoMetadata#73
• Show all articles of an issue or a journal on a timeline TIBHannover/geoMetadata#74
• Add a map icon to issue page that highlights the geometries on hover and opens the pop-up on the map on click TIBHannover/geoMetadata#158
• Highlight multiple issue toc entries for overlapping geometries TIBHannover/geoMetadata#159

For every feature, first create a matching issue for Janeway, then check if the feature is not already (partially) implemented, only then begin implementation/testing/etc.