Added the option WRITE_FILTERED_DATA to write time filtered measured data to disk.
If WRITE_FILTERED_DATA is not set in the JSON file, it will be set to 0.

Added debugging output for VP and renamed some variables to be consistent within the code.

Removed all checkpointing things in the code.

Removed the option HESSIAN from the code.

Workflow file now includes a header.

Update: Merge test

For the exchange of the wavefields a wrapping layer of FDORDER/2 is needed.
Nevertheless a wrapping layer of FDORDER/2 +1 was implemented because of undetected errors in the exchange functions.

Added taper for inverted source time function (use switch TAPER_STF, see taper.c for definition) and individual time windowing (use switch TW_IND, then three columns are expected in PICK_FILE for each trace with picked time - twl plus - twl minus, in this case TWLENGTH_PLUS and TWLENGTH_MINUS are ignored). Time windowing is now also applied during the inversion of the source time function.