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/hex_to_rgba.py

@@ -0,0 +1,22 @@
+def hex_to_rgba(hex_color):
+    """
+    Convert hex(a) to rgba
+    :param hex_color: input value
+    """
+
+    try:
+        if len(hex_color) in range(6, 10):
+            hex_color = hex_color.lstrip('#') + "ff"
+            # if is convertable
+            int(hex_color[:], 16)
+        else:
+            raise ValueError
+
+    except ValueError:
+        raise ValueError(f'Error: Invalid HEX color code: {hex_color}')
+
+    else:
+        return int(hex_color[0:2], 16), \
+            int(hex_color[2:4], 16), \
+            int(hex_color[4:6], 16), \
+            int(hex_color[6:8], 16) / 255