add some links to doc

Author: SethTisue

doc/genesis.md

@@ -430,3 +430,7 @@ Add a webhook via https://github.com/scala/scala/settings/hooks/new:
 - they are tricky to access, might disappear,...
 - checksum is computed with `shasum -a 256`
 - TODO: host them on an s3 bucket (credentials are available automatically)
+
+# Recreating Jenkins master
+
+see [recreate-jenkins-master.md](recreate-jenkins-master.md)

doc/overview.md

@@ -204,3 +204,4 @@ The architecture is inspired by https://erichelgeson.github.io/blog/2014/05/10/a
   locally
 * [genesis.md](genesis.md): how the infrastructure was initially
   created, and how to re-create it if needed
+     * [recreate-jenkins-master.md](recreate-jenkins-master.md)