concNav label between menu for switchConc and switchMov

[riedde]

There is the possibility to have a label in the concordanceNav that expresses something like Satz/Movement. This is provided by the following code as the first child of <groups>

<names>
    <name xml:lang="de">Satz</name>
    <name xml:lang="en">Movement</name>
</names>

Issue: If this isn't set, the following function will deliver all names of all descendant group elements! https://github.com/Edirom/Edirom-Online/blob/f1ef943a200500de66a8379f51bb007be1d5ced1/app/view/window/concordanceNavigator/ConcordanceNavigator.js#L288