Make scripts generic and fix several bugs

- Add optional directory argument to images_resize_recursive.sh,
  zip_images_resize_recursive.sh, and new rar2zip_recursive.sh
- Remove hardcoded-path wrappers rar2zip_images.sh and rar2zip_incomplete.sh
- Fix zip_images_resize.sh: move SCRIPT_DIR to top, change exit 1 to
  continue on bad output file so remaining files still process
- Use MAX_PIXELS variable in images_resize.sh resize argument
- Fix zip_images_recursive.sh: replace case-sensitive 7z globs with
  find -iregex piped via xargs

images_resize_recursive.sh

@@ -1,8 +1,16 @@
 #!/bin/bash
 
+SEARCH_DIR="${1:-.}"
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 
-find . -mindepth 1 -type d -print0 | while IFS= read -r -d '' f
+if [ ! -d "$SEARCH_DIR" ]; then
+    echo "Error: '$SEARCH_DIR' is not a directory"
+    exit 1
+fi
+
+echo "Resizing images recursively in $SEARCH_DIR"
+
+find "$SEARCH_DIR" -mindepth 1 -type d -print0 | while IFS= read -r -d '' f
 do
     if pushd "$f" > /dev/null; then
         "$SCRIPT_DIR/images_resize.sh"