Delay loading of geometry/meta data

[plepe]

When not needing geometry/meta data (e.g. when doing relationship queries), do not load geometry/meta data. Add function which loads geometry/meta data later, when requested.

[plepe]

TODO:

• eval functions (and other functions) which need geometry need to check if geometry is loaded
• check for geometry needs to be done before eval function is called
• update DB-functions, so that geometry does not get loaded per default (not for main objects_bbox() though)
• add function (or modify objects_by_id()) function to download geo et.al.
• update documentation