Switch from biased interpolations to reducing the order of
interpolations near surfaces
Only change igc, jgc if spatialorder=2
Only use 4th order interpolation for the advected quantity
Merge remote-tracking branch 'upstream/master' into 2i4

Conflicts:
	src/advec_2i4.cxx
Cleanup, leave the other old functions for now for testing purposes
Added base state density to 2i4 advection
Added cuda version of 2i4 advection
Merge branch 'masterupstream' into templates