RFC: New function for operating with core.Namespace

[marcin-krolik]

When dealing with more then one static element following dynamic element one need to "spam" AddStaticElement(element string) function.
I propose to introduce new function to add possibility to add arbitrary number of static elements

func (n Namespace) AddStaticElements(values ...string) Namespace {
    for _, value := range values {
        n = append(n, NamespaceElement{Value: value})
    }
    return n
}

[jcooklin]

👍

[tiffanyfay]

Fixed by #885