v6.0-beta.18

* Issue **#981** : Fixed dashboard deletion

* Issue **#989** : Upgraded stroom-expression to v1.4.13 to add new dashboard `link` function.

* Issue **#988** : Changed `generate-url` XSLT function to `link` so it matches the dashboard expression. Changed the parameters to create 4 variants of the function to make creation of simple links easier.

* Issue **#980** : Fix for NPE when fetching dependencies for scripts.

* Issue **#978** : Re-ordering the fields in stream data source

* Issue **gchq/stroom-content#31** : Uplift stroom-logs content pack to v2.0-alpha.5.

* Issue **#982** : Stop proxy trying to health check the content syncing if it isn't enabled.

* Change error logging in ContentSyncService to log stack trace

* Uplift send_to_stroom.sh in the distribution to v2.0

* Issue **#973** : Export servlet changed to a Resource API, added permission check, improved error responses.