Enable reloading modules

Useful for modules like pretty.sh so that they can benefit from safety and
simplicity of having default but app can still reload it.

Note that in most cases using sfpi is cleaner and does not need
reloading, but pretty.sh is using dumb way of loading.

src/shellfu.sh.skel

@@ -173,6 +173,19 @@ shellfu() {
                 shellfu __die "cannot import module: $mname"
             fi
             ;;
+        reload)
+            #
+            # Reload module named $1 (unsafe!)
+            #
+            local mname=$1
+            shellfu _is_imported "$mname" || {
+                shellfu __warn "cannot reload; not imported yet: $mname"
+                return 2
+            }
+            if ! shellfu _do_import "$mname"; then
+                shellfu __die "cannot reload module: $mname"
+            fi
+            ;;
         try_import)
             #
             # Try if module $1 could be imported