Merge branch '5-implement-convergence-study' into 'master'

FWI/conf/GridStudy.conf

FWI/src/FWIHelpers.cpp

FWI/src/FWIRandomMains.cpp

FWI/src/FWI_DGTS.cpp

FWI/src/Main.cpp

tools/ConvergenceTools/Combine.py

tools/ConvergenceTools/CreateNetSource.py

tools/ConvergenceTools/ReceiverSourceCreator.py

tools/ConvergenceTools/RunCalcsNetReproc.sh

tools/ConvergenceTools/acoustic_exact_solution_2D_conv.py

tools/ConvergenceTools/seismogram_lib_conv.py