fix #2336: support for secondary users in multi-users mode
fix #2336: support for secondary users in multi-users mode

This will allow c:geo to work correctly in multi-users mode as long as
the default settings (keep files on internal sd card or phone memory)
are used.

Files stored on secondary memory will still be shared between users,
but the permissions should be allowing that.

pstorch/cgeo,ThibaultR/cgeo,lewurm/cgeo,mucek4/cgeo,madankb/cgeo,SammysHP/cgeo,schwabe/cgeo,xiaoyanit/cgeo,tobiasge/cgeo,yummy222/cgeo,samueltardieu/cgeo,kumy/cgeo,S-Bartfast/cgeo,mucek4/cgeo,pstorch/cgeo,yummy222/cgeo,Huertix/cgeo,pstorch/cgeo,samueltardieu/cgeo,vishwakulkarni/cgeo,brok85/cgeo,superspindel/cgeo,xiaoyanit/cgeo,KublaikhanGeek/cgeo,KublaikhanGeek/cgeo,S-Bartfast/cgeo,lewurm/cgeo,cgeo/cgeo,Huertix/cgeo,matej116/cgeo,brok85/cgeo,cgeo/cgeo,ThibaultR/cgeo,auricgoldfinger/cgeo,yummy222/cgeo,cgeo/cgeo,vishwakulkarni/cgeo,madankb/cgeo,matej116/cgeo,schwabe/cgeo,samueltardieu/cgeo,mucek4/cgeo,rsudev/c-geo-opensource,KublaikhanGeek/cgeo,S-Bartfast/cgeo,superspindel/cgeo,lewurm/cgeo,cgeo/cgeo,Huertix/cgeo,kumy/cgeo,auricgoldfinger/cgeo,marco-dev/c-geo-opensource,rsudev/c-geo-opensource,ThibaultR/cgeo,tobiasge/cgeo,Bananeweizen/cgeo,rsudev/c-geo-opensource,brok85/cgeo,vishwakulkarni/cgeo,SammysHP/cgeo,schwabe/cgeo,tobiasge/cgeo,auricgoldfinger/cgeo,marco-dev/c-geo-opensource,SammysHP/cgeo,matej116/cgeo,madankb/cgeo,marco-dev/c-geo-opensource,Bananeweizen/cgeo,kumy/cgeo,xiaoyanit/cgeo,Bananeweizen/cgeo,superspindel/cgeo,schwabe/cgeo