Compilation error when WITH_EXPLICIT_DISSIPATION is enabled fixed
Concentration field added

Need to be tested and added as well in timestep_compressible
Compilation error when COMPRESSIBLE is enabled fixed
Merge branch 'master' into concentration
Python script for reading and displaying spectra
Magnetic spectra not displayed when empty
Timevar-reading script
New system of spectrum output
Merge branch 'master' into concentration
Application of the new spectrum output system to the concentration
New spectrum system handled (+ conversion from the old one)
Script reading VTK files added
Header now in the right order after spectrum conversion
Computation of integral length scales added
Small-Péclet-number approximation implemented
Sign error fixed
Default parameters/defines updated
Default problem updated
Psi field added to VTK files
Merge branch 'concentration'

Conflicts:
	src/common.c
	src/common.h
	src/documentation.h
	src/mainloop.c
	src/output/output_spectrum.c
	src/output/output_timevar.c
	src/problem/default/gvars.h
	src/problem/default/snoopy.cfg
	src/snoopy.c
	src/snoopy.h