Introduce hierarchical order for groups

[Feilner]

Until now only the direct parent is shown in braces after the title. In a hierarchical structure with several levels that's not sufficient. because e.g. in the following structure within Volkszähler

my building                                  (type building)
|- 1st floor                                 (type group)
|    |- bathroom                             (type group)
|    |    |- temperature                     (type sensor)
|    |    \- humidity                        (type sensor)
|    \- sleeping room                        (type group)
|         |- temperature                     (type sensor)
|         \- humidity                        (type sensor)
\- 2nd floor                                 (type group)
     \- bathroom                             (type group)
          |- temperature                     (type sensor)
          \- humidity                        (type sensor)

The generated entries would be:

 humidity (bathroom)
 humidity (bathroom)
 humidity (sleeping room)
 temperature (bathroom)
 temperature (bathroom)
 temperature (sleeping room)

Therefore this change creates a folder like structure for groups where this entries become to:

my building\1st floor\bathroom\humidity
my building\1st floor\bathroom\temperature
my building\1st floor\sleeping room\humidity
my building\1st floor\sleeping room\temperature
my building\2nd floor\bathroom\humidity
my building\2nd floor\bathroom\temperature

[andig]

Perfekt, vielen Dank!