Fix up install location

The dh_auto_install rule was placing its output in the wrong place for
some reason (and also wasn't generating a separate Python 3-based
install). This override fixes the issue, so that the pi can now produce
valid python 2 and 3 binary deb packages

debian/rules

@@ -7,6 +7,10 @@ export DH_OPTIONS
 %:
 	dh $@ --with python2,python3,sphinxdoc --buildsystem=python_distutils
 
+override_dh_auto_install:
+	python setup.py install --root debian/python-picamera --install-layout=deb
+	python3 setup.py install --root debian/python3-picamera --install-layout=deb
+
 override_dh_auto_test:
 	# Don't run the tests!