Python: Import Customizations into python

Using the pattern from JS and Java to make this the _first_ import in `<lang>.qll`

Author: RasmusWL

python/ql/src/semmle/python/Customizations.qll renamed to python/ql/src/Customizations.qll

@@ -1,3 +1,4 @@
+import Customizations
 import semmle.python.Files
 import semmle.python.Operations
 import semmle.python.Variables