adding dump_type 'displ_only' to field_transform
construct sem/fem/midpoint mesh for kwf output & preparing netcdf file
removing unused var
write midpoint mesh to file (untested)
local output file only written with verbose > 1
need to create mapping even when wavefields are not dumped, because elastic parameters

are dumped always when netcdf is on - no idea why that is though
removing bug from previous commit
midpoint mesh output + xdmf now working
adding output for sem + fem meshes + xdmf files
Merge branch 'master' of https://github.com/geodynamics/axisem