Hazard Getters optimization (grid spacing)

[matley]

Currently, the user can provides a an ```hazard_maximum_distance``` parameter to exclude hazard values too far to be considered for risk analysis.

As a matter of fact, this parameter has a big impact on the performance of the hazard getters. However, the default value of 10km is a really pessimistic. When the hazard values given in input are computed on a grid, it is safe to use the region spacing of the hazard calculation, those values are computed from.