docs: added docs archive for v4.3

docs/VERSION

@@ -1 +1 @@
-v4.2
+v4.3

docs/sources/archive.md

@@ -13,6 +13,7 @@ Here you can find links to older versions of the documentation that might be bet
 of Grafana.
 
 - [Latest](http://docs.grafana.org)
+- [Version 4.3](http://docs.grafana.org/v4.3)
 - [Version 4.2](http://docs.grafana.org/v4.2)
 - [Version 4.1](http://docs.grafana.org/v4.1)
 - [Version 4.0](http://docs.grafana.org/v4.0)