compare.py should show max error location in limited output

[phmarti]

When running compare.py it only shows a limited number of values by default. These values should bracket the maximum values to help assessing how bad the error actually is. Below is an example to illustrate the issue:

Failed values (displayed 10 of 3844):
(0, 2): value_1 = -14.0368651081, value_2 = -14.0368651063, error = 1.2689171486e-10
(1, 2): value_1 = 7.5062468938, value_2 = 7.5062468958, error = 2.7428688491e-10
(2, 2): value_1 = -20.6270772118, value_2 = -20.6270772100, error = 8.6545724085e-11
(3, 2): value_1 = -27.9763234801, value_2 = -27.9763234781, error = 7.3193614693e-11
(4, 2): value_1 = 51.8431722790, value_2 = 51.8431722808, error = 3.5319652721e-11
(5, 2): value_1 = 29.2386382685, value_2 = 29.2386382706, error = 7.2982504510e-11
(6, 0): value_1 = -19.2101080984, value_2 = -19.2101080981, error = 1.6434490985e-11
(6, 2): value_1 = 59.3551172720, value_2 = 59.3551172736, error = 2.7259504298e-11
(7, 2): value_1 = -7.2697008878, value_2 = -7.2697008859, error = 2.5670169949e-10
(8, 2): value_1 = -79.9826766660, value_2 = -79.9826766636, error = 2.9390503836e-11
Number of errors: 3844
Number of NaN: 0
Percentage of errors: 6.26 %
Maximum absolute error: 1.5792431032e-02
Maximum relative error: 2.8707840737e-04

The errors that are explicitly shown are fine, but there are values with much larger errors (O(1e-4)).