FIXES #802 by adding the additional connection operators

* `Connections.branch()`
* `Connections.root()`
* `Connections.potentialRoot()`
* `Connections.isRoot()`
* `Connections.rooted()`
* `rooted()` with deprecation notice

git-svn-id: https://svn.modelica.org/projects/Modelica/trunk@6309 7ce873d0-865f-4ce7-a662-4bb36ea78beb