[examples] README.md files modified and general cleanup. Add new setup

README.md

examples/1ptracer/README.md

examples/1ptracer/doc/intro.md

examples/1ptracer/doc/results.md

examples/1ptracer/img/setup.svg

examples/1ptracer/main.cc

examples/1ptracer/problem_1p.hh

examples/1ptracer/problem_tracer.hh

examples/1ptracer/spatialparams_1p.hh

examples/1ptracer/spatialparams_tracer.hh

examples/2pinfiltration/README.md

examples/2pinfiltration/doc/.gitkeep

examples/2pinfiltration/doc/intro.md

examples/2pinfiltration/doc/results.md

examples/2pinfiltration/img/.gitkeep

examples/2pinfiltration/main.cc

examples/2pinfiltration/problem.hh

examples/2pinfiltration/spatialparams.hh

examples/README.md