Introduce 'Plugins' plugin to embed external services

Change-Id: Iffc71635c27ceec91fc1beef248d79f56adcad17
diff --git a/.gitignore b/.gitignore
index aeb6634..53dd354 100644
--- a/.gitignore
+++ b/.gitignore
@@ -33,6 +33,7 @@
 *.sqlite
 *.log
 *.db
+*.plugins.json
 *.old
 .*
 /t/kalamar_user_client.t