tree-wide: use proper unicode © instead of (C) where we can

Let's use a proper unicode copyright symbol where we can, it's prettier.

This important patch is very important.
diff --git a/test/create-sys-script.py b/test/create-sys-script.py
index 33a4d31..d03ca2c 100755
--- a/test/create-sys-script.py
+++ b/test/create-sys-script.py
@@ -6,7 +6,7 @@
 #
 # create-sys-script.py
 #
-# (C) 2017 Canonical Ltd.
+# © 2017 Canonical Ltd.
 # Author: Dan Streetman <dan.streetman@canonical.com>
 """