[homekit] add support for group switches

[yfre]

as discussed here
https://community.openhab.org/t/problems-with-homekit-switchable-feature-on-switch-groups/100702
and here
https://community.openhab.org/t/homekit-could-not-find-existing-mac/100845/26

current HomeKit binding does not support groups with a base item, eg.

Group:Switch:OR(ON,OFF) gLights "ALL Lights [%s]"	{homekit="Lighting"}
Switch Light_1 "Light 1 [%s]"  (gLights,) {homekit="Lighting"}
Switch Light_2 "Light 2 [%s]"  (gLights,) {homekit="Lighting"}

it would create only one accessory - for the group but not for light_1 and light_2. the logic is following: if an item is part of bigger group with homekit tag, then the item is a characteristic of this homekit accessory/group.

this PR fix this issue by ignoring groups with base item.

Signed-off-by: Eugen Freiter freiter@gmx.de

[TravisBuddy]

Travis tests have failed

Hey @yfre,
please read the following log in order to understand the failure reason. There might also be some helpful tips along the way.
It will be awesome if you fix what is wrong and commit the changes.

[TravisBuddy]

Travis tests have failed

Hey @yfre,
please read the following log in order to understand the failure reason. There might also be some helpful tips along the way.
It will be awesome if you fix what is wrong and commit the changes.

[cpmeister]

LGTM