Create a new ErrorEstimator type thorn which can set up given number of levels and their extents.

[shankar-1729]

In the new thorn, user defines the number of levels (which may be less than max_num_levels). The user also sets the extent of each level (radial/cuboidal). For example:

ErrorEstimatorNew::coarse_resolution = 64   
ErrorEstimatorNew::max_num_levels = 9
ErrorEstimatorNew::current_num_levels = 6
ErrorEstimatorNew::radius[0] = 2048
ErrorEstimatorNew::radius[1] = 1024
ErrorEstimatorNew::radius[2] = 512
ErrorEstimatorNew::radius[3] = 400
ErrorEstimatorNew::radius[4] = 160
ErrorEstimatorNew::radius[5] = 80

The parameters current_num_levels and radius[i] should be steerable always.