Add extent troubleshooting to maps documentation

[MarcelGeo]

Possible issues for users
If there is no area of interest for current project displayed in dashboard, use project settings directly in QGIS. This can be particularly problematic for large-scale projects, as it makes it difficult to locate important features within the web maps. It would be good to mention options for setting the extent in QGIS. These settings are connected with maps in dashboard.

Under the hood is our system looking for projects extent in three options:

• Project settings -> View settings
  
• Project settings -> QGIS server
  
• If above extends are not checked , extent is calculated from all layers.

We will change ordering of extent calculation, where specially for maps will be qgis server extent prioritized over view settings. There should be then different extent for mobile and maps.