Implement salt states for gva webinterface

- setup listener and pg_hba.conf for PostgreSQL server
- add state code for gva
- add macros for nginx and uwsgi with Python 3 support
- add pillar data for gva

states/uwsgi/init.sls

@@ -0,0 +1,8 @@
+uwsgi:
+  pkg:
+    - installed
+  service.running:
+    - enable: True
+    - reload: True
+    - require:
+      - pkg: uwsgi

states/uwsgi/python3.sls

@@ -0,0 +1,7 @@
+include:
+  - uwsgi
+
+uwsgi-plugin-python3:
+  pkg.installed:
+    - require_in:
+      - service: uwsgi