Allow offline search with any map

[steed]

The offline search capabilities of the OpenAndroMaps POI databases are exceptionally useful.



Since the search is restricted to the area shown on the screen, it would be useful for any map. Any offline map can benefit from such a search capability. In fact, it can also be useful as an alternative for the Google search when using an online map.



It would be great if OruxMaps maintains a list containing the "coverage area" for every POI database, and allows offline search in the appropriate database/s whenever there is an overlap between a "coverage area" and the area shown on the screen.