reorders EXAMPLES/ and utils/ folder with new sections; updates doc, readmes and checks #168

Job	Run time
Check file changes	26s
Test on Mac	14m 48s
Test Intel on ubuntu-20.04	5m 58s
Test on ubuntu-latest	2m 55s
Test on ubuntu-20.04	3m 47s
Test run example 3 - layered halfspace	3m 25s
Test run example 1 - meshfem3D simple model	3m 47s
Test run example 0 - make tests	6m 47s
Test run example 10 - homogeneous halfspace	2m 57s
Test run example 2 - fault tpv5	5m 23s
Test run example 11 - poroelastic	3m 20s
Test run example 4 - small adjoint	3m 32s
Test run example 5 - socal1D	3m 27s
Test run example 6 - socal1D 1d_socal	4m 50s
Test run example 7 - socal1D 1d_prem	3m 12s
Test run example 8 - socal1D 1d_cascadia	3m 44s
Test run example 9 - coupling FK	4m 59s
Test run example 12 - PML elastic	2m 46s
Test run example 13 - PML acoustic	3m 14s
Test run example 14 - waterlayered halfspace	3m 39s
Test run example 15 - tomographic model	2m 48s
Test run example 16 - cavity	2m 37s
Test run example 17 - sep bathymetry	5m 8s
	1h 37m 29s

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