bugfixes and improved themeing support

src/sh/config.sh

@@ -1,4 +1,5 @@
-if [ "${CONFIGFILE:-}" ]; then
-  [ ! -f "$CONFIGFILE" ] && err "Configuration $CONFIGFILE not found." && exit 1
-  . "$CONFIGFLIE"
-fi
+CONFIGFILE_DEFAULT="$HOME/.config/$APP_NAME/config"
+CONFIGFILE="${CONFIGFILE:-"$CONFIGFILE_DEFAULT"}"
+[ "$CONFIGFILE" != "$CONFIGFILE_DEFAULT" ] && [ ! -f "$CONFIGFILE" ] && err "The configuration file manually specified with the environment variable CONFIGFILE=($CONFIGFILE) does not exist." && exit 1
+# shellcheck source=/dev/null
+[ -f "$CONFIGFILE" ] && . "$CONFIGFILE"