WIP: Exclude accessions where geo.uncertainty > 20000

In AccessionGeo the uncertainty declares how "bad" the coordinates are (in m meters). Such accessions should not be included in GIS functions of Genesys.

Add a constant ACCEPTABLE_COORD_UNCERTAINTY = 20000 (20km). Latitude/longitude of accessions with uncertainty over this constant must:

1. Not be included in the map tiles generated by Genesys
2. Not display the map in the website UI (the data should be displayed)
3. Excluded when lookup is done by lat/lon from UI
4. PDCI calculator should assign 0 value