Query: automatically update index statistics to get better cost estimates

The indexes don't currently have good cost estimates, so that in many cases the best index is not used. The cost estimation of the indexes needs statistics (for example, how many entries are in an index, or how many entries are stored in a index key). It should be possible to implement auto-update of statistics for the node type index, the property index, and the ordered index. Possibly, this could be done asynchronously.