Export/import resources

[lstocchi]

Now that we are switching to having the tree with a single namespace it would be good if we could export/import resources.

First idea is to add two actions, one to export a resource as a file and the second to import a file
Second idea is to generalize the Hub Panel or create a new one where the user can add the config to login to another cluster/namespace and there see the list of all pipelines/tasks belonging to that cluster and select the resources to be imported/copied in the current one.