Merging defect fixes from branch 3.2.x to the trunk

[Badreddine.Karoui@…]

The following fixes need to be merged from branch 3.2.x to the trunck: 1) Iterating through all the features of a large SDF file causes a significant loss of the system available memory. This is due to the system disk cache which tend to use all the memory it can get. The fix is to remove the random access option when opening the SDF file. That reduced the memory used by the disk cache to a reasonable amount and did not impact the performance of the SDF provider(it actually helped a bit). 1) An Rtree rebalancing issue where the root node get deleted and the new root node is not persisted.