GNOME dependable installation, structure and style improvements

Split utils in utils.py to a directory
Moved ./gnome-shell_css/ to ./gnome-shell/.css/

scripts/utils/replace_keywords.py

@@ -0,0 +1,19 @@
+def replace_keywords(file, *args):
+    """
+    Replace file with several keywords
+    :param file: file name where keywords must be replaced
+    :param args: (keyword, replacement), (...), ...
+    """
+
+    # skip binary files in project
+    if not file.lower().endswith(('.css', '.scss', '.svg')):
+        return
+
+    with open(file, "r") as read_file:
+        content = read_file.read()
+
+    for keyword, replacement in args:
+        content = content.replace(keyword, replacement)
+
+    with open(file, "w") as write_file:
+        write_file.write(content)