[FSS0] Add Fusee secondary storage parser

Using "fss0={sd path}" allows you to parse kips, exosphere and warmboot from a fusee secondary binary.

Exosphere and warmboot are overridable if these entries are defined after that.

Additionally any extra kip can be loaded as before via
kip1={sd path}/* for many
or
kip1={sd path} for a sigle one

Warning: Don't double load core kips like loader, pm, sm and ams_mitm. The result will be a hang.

Makefile

@@ -48,7 +48,7 @@ OBJS += $(addprefix $(BUILDDIR)/$(TARGET)/, \
 # Horizon.
 OBJS += $(addprefix $(BUILDDIR)/$(TARGET)/, \
 	nx_emmc.o \
-	hos.o hos_config.o pkg1.o pkg2.o secmon_exo.o sept.o \
+	hos.o hos_config.o pkg1.o pkg2.o fss.o secmon_exo.o sept.o \
 )
 
 # Libraries.