BSPC: Fix reading BSPs from pk3s
BSPC: Fix creating maps directory for .aas of a zipped .bsp

bspc -bsp2ass pak0.pk3/maps/*.bsp now creates maps directory instead of erroring when it doesn't exist.
BSPC: Don't make created directories r/w to all users
BSPC: Remove reference to pak and sin files

Support for reading files from them has already been removed.