Serverproxy manager (#61)

* Create serverproxy_manager.py

* Replace use of direct RenderServerProxy with ServerProxyManager method

src/api/serverproxy_manager.py

@@ -0,0 +1,16 @@
+from src.api.server_proxy import RenderServerProxy
+
+
+class ServerProxyManager:
+
+    server_proxys = {}
+
+    @classmethod
+    def get_proxy_for_hostname(cls, hostname):
+        found_proxy = cls.server_proxys.get(hostname)
+        if not found_proxy:
+            new_proxy = RenderServerProxy(hostname)
+            new_proxy.start_background_update()
+            cls.server_proxys[hostname] = new_proxy
+            found_proxy = new_proxy
+        return found_proxy