[test][2p] Dissolve implicit folder

test/porousmediumflow/2p/CMakeLists.txt

test/porousmediumflow/2p/adaptive/CMakeLists.txt

test/porousmediumflow/2p/adaptive/initialsolutionbox.txt

test/porousmediumflow/2p/adaptive/initialsolutioncc.txt

test/porousmediumflow/2p/adaptive/main.cc

test/porousmediumflow/2p/adaptive/params.input

test/porousmediumflow/2p/adaptive/pointsourceproblem.hh

test/porousmediumflow/2p/adaptive/problem.hh

test/porousmediumflow/2p/boxdfm/CMakeLists.txt

test/porousmediumflow/2p/boxdfm/grids/durlofsky.geo

test/porousmediumflow/2p/boxdfm/grids/durlofsky.msh

test/porousmediumflow/2p/boxdfm/grids/quads_2d.geo

test/porousmediumflow/2p/boxdfm/grids/quads_2d.msh

test/porousmediumflow/2p/boxdfm/grids/tets_3d.geo

test/porousmediumflow/2p/boxdfm/grids/tets_3d.msh

test/porousmediumflow/2p/boxdfm/main.cc

test/porousmediumflow/2p/boxdfm/params.input

test/porousmediumflow/2p/boxdfm/problem.hh

test/porousmediumflow/2p/boxdfm/spatialparams.hh

test/porousmediumflow/2p/cornerpoint/CMakeLists.txt