Add generic config file finder

This should be useful for cases when a sub-command wants to maintain
non-INI config locations.

src/saturnin.sh.skel

@@ -180,6 +180,32 @@ saturnin__conf() {
     return "${PIPESTATUS[0]}"
 }
 
+saturnin__conf_find() {
+    #
+    # Find all existing instances of sub-path $1 on $SATURNIN_CONF_PATH
+    #
+    # Go through all elements of $SATURNIN_CONF_PATH, looking for file
+    # on sub-path $1.  Print each existing path, ignore rest.
+    #
+    # If at least one path was found, return zero.  Otherwise, return one,
+    # or more in case of error.
+    #
+    local file=$1       # sub-path to find
+    local trydir        # each item of $SATURNIN_CONF_PATH
+    local trypath       # each combined path
+    debug -v SATURNIN_CONF_PATH
+    echos "$SATURNIN_CONF_PATH" \
+      | tr ':' '\n' \
+      | while read -r trydir;
+        do
+            test -n "$trydir" || continue
+            trypath="$trydir/$file"
+            test -e "$trypath" || continue
+            echos "$trypath"
+        done \
+      | grep .
+}
+
 saturnin__get() {
     #
     # Show Saturnin Internal info by key $1 and exit