Custom Label for filter_bar filters

[acs]

We are using a filter_bar to restrict the context to a concrete index (the global index is an alias joining several indices) in a dashboard. The idea commented by @rashidkpc in #1606. We have created this filter using the dashboard editor and it works great. But the button for it contains the filter query.

It will be great to include in the filter editor a label field which is used instead the filter definition if exists. Pretty related to #3621.

[rashidkpc]

Closely related to #1583