Corrections to avoid excesive memory usage (request_url in blocks of 100).
Corrections in MBtilesAsync which should now be stable. New logic for creation of SpatialVectorTable tables in SpatialiteDatabaseHandler.
Merge branch 'mbtiles' of https://github.com/mj10777/geopaparazzi into mj10777-mbtiles
merge + addition of last minute fixes for bad http requests and OSM tiles bounds check
load maps in background with a progress dialog