Merge branch 'disc_patch_x' into 'master'
Disc patch x Replaced disc patch potential in z with a disc patch potential in x. Added a 1D version of the disc patch test. Changed the GIZMO time step criterion (fixed a bug in the original criterion, and tried to make the criterion stricter to cope with the disc patch potential). Removed some gravity variables that were no longer used. Put the flux limiter in a separate file and made it configurable. See merge request !382