Added mesh files for full support on other machines

.gitignore

src/channel_periodic.msh

src/example_nucleus/grids/channel_periodic.msh

src/example_nucleus/grids/rectangle_periodic.msh

src/example_nucleus/grids/rectangle_periodic_coarse.msh

src/example_nucleus/grids/square_periodic.msh

src/paper_epsdelta/grids/rectangle_periodic.msh

src/paper_epsdelta/grids/rectangle_periodic_coarse.msh

src/paper_epsdelta/grids/square_periodic.msh

src/paper_thinstrip_full/thinstrip_periodic.msh

src/paper_thinstrip_mixed/grids/channel_periodic.msh

src/paper_thinstrip_mixed/grids/rectangle_periodic.msh

...paper_thinstrip_mixed/grids/rectangle_periodic_coarse.msh

src/paper_thinstrip_mixed/grids/square_periodic.msh

src/paper_thinstrip_mixed/grids/thinstrip_coarse_1_2.msh

src/paper_thinstrip_mixed/grids/thinstrip_coarse_1_4.msh

src/paper_thinstrip_mixed/grids/thinstrip_coarse_1_8.msh

src/pntest/grids/square_periodic.msh

src/rectangle_periodic_coarse.msh

src/summerschool.msh