Prepare support for multiple plugins

tasks/alerta.yml

@@ -121,14 +121,16 @@
     dest: /tmp/{{ item }}
   with_items:
     - alerta_gitlab.py
-    - setup.py
+    - setup_alerta_gitlab.py
   tags:
     - plugin
 
 - name: Install Gitlab plugin
-  command: python3 setup.py install
+  command: python3 setup_{{ item }}.py install
   args:
     chdir: /tmp
+  with_items:
+    - alerta_gitlab
   tags:
     - plugin