fix #3464, terrain filter up to 7
fix #3464, terrain filter up to 7

This is just an increase of the global filter range. The available
filters do not depend on which connectors are active.
tobiasge/cgeo,S-Bartfast/cgeo,superspindel/cgeo,schwabe/cgeo,marco-dev/c-geo-opensource,schwabe/cgeo,vishwakulkarni/cgeo,madankb/cgeo,kumy/cgeo,matej116/cgeo,yummy222/cgeo,superspindel/cgeo,brok85/cgeo,pstorch/cgeo,SammysHP/cgeo,xiaoyanit/cgeo,cgeo/cgeo,tobiasge/cgeo,schwabe/cgeo,matej116/cgeo,pstorch/cgeo,matej116/cgeo,pstorch/cgeo,mucek4/cgeo,mucek4/cgeo,KublaikhanGeek/cgeo,brok85/cgeo,ThibaultR/cgeo,lewurm/cgeo,Huertix/cgeo,Bananeweizen/cgeo,Bananeweizen/cgeo,marco-dev/c-geo-opensource,SammysHP/cgeo,lewurm/cgeo,Huertix/cgeo,S-Bartfast/cgeo,madankb/cgeo,schwabe/cgeo,KublaikhanGeek/cgeo,tobiasge/cgeo,samueltardieu/cgeo,vishwakulkarni/cgeo,madankb/cgeo,rsudev/c-geo-opensource,marco-dev/c-geo-opensource,cgeo/cgeo,SammysHP/cgeo,auricgoldfinger/cgeo,yummy222/cgeo,yummy222/cgeo,mucek4/cgeo,superspindel/cgeo,rsudev/c-geo-opensource,KublaikhanGeek/cgeo,kumy/cgeo,xiaoyanit/cgeo,cgeo/cgeo,auricgoldfinger/cgeo,Huertix/cgeo,vishwakulkarni/cgeo,rsudev/c-geo-opensource,samueltardieu/cgeo,cgeo/cgeo,S-Bartfast/cgeo,auricgoldfinger/cgeo,ThibaultR/cgeo,samueltardieu/cgeo,kumy/cgeo,Bananeweizen/cgeo,ThibaultR/cgeo,brok85/cgeo,xiaoyanit/cgeo,lewurm/cgeo