GitLab

Added a new switch FDORDER_TIME to use a fourth order accurate temporal FD-scheme. This is realized with the Adams-Bashforth method.
Possible values for FDORDER_TIME are 2 and 4, whereas 2 refers to the classical leapfrog scheme.

TSNAP2 will be set to TIME if TSNAP>TIME. ( Time is recalculated to TIME=NT*DT in sofi3D.c and thus can differ to TIME given in .json. So even if TIME and TSNAP2 are equal in .json they can differ in the checkfd functions)

1. added derivation of the explosive source. This is necessary because the explosive source will be read in after the wavefield updates. Also the scaling of the explosive source is now corrected. 2. RSG isn't implemented in the current release