Add simpler examples #128

Job	Run time
Check file changes	15s
Test on Mac	10m 58s
Test Intel on ubuntu-20.04	8m 44s
Test on ubuntu-latest	1m 7s
Test on ubuntu-20.04	1m 32s
Test run example 3 - benchmark claerbout kernel elastic SH	2m 43s
Test run example 0 - make tests	2m 56s
Test run example 1 - benchmark claerbout kernel acoustic	2m 31s
Test run example 2 - benchmark claerbout kernel elastic P-SV	2m 31s
Test run example 10 - simple_topography_and_also_a_simple_fluid_layer debug double_precision	2m 7s
Test run example 4 - benchmark claerbout kernel acoustic-elastic	2m 41s
Test run example 5 - moving sources	1m 45s
Test run example 6 - anisotropy	1m 29s
Test run example 7 - Industrial_Format_SEP	4m 21s
Test run example 8 - axisymmetric_case_AXISYM_option	1m 52s
Test run example 9 - simple_topography_and_also_a_simple_fluid_layer debug	2m 30s
Test run example 11 - tomographic_ocean_model	1m 35s
Test run example 12 - Marmousi2	2m 4s
	53m 41s

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