Support for multiple relays

[frenchie71]

Allow a configurable number of relays.

Use case

I have two garage doors but only one RFID reader. Some codes should open the right door, some the left door and maybe some should open both doors.

Possible use case might be as well switching on a light or signal etc.

Interface and downstream compatibility

The number of relays can be configured in the UI, the maximum number of relays is currently hard coded to 4 but can easily be changed. For the official board the number is hard coded to 1.

The settings names for the first relay have not been changed in order to provide downstream compatibility to previous releases. For each additional relay a node is appended to the hardware node

The user forms and files have been amended in order to reflect access rights to a specific relay

Known issues:

• on User access, multiple entries are created in the access log - one for each relay. At this point the log does not contain information of which relay has been accepted and which has been denied
• If a user has access to only some relays, a denied message will be entered in the event log for each additional relay
• MQTT open door command only opens the first relay

[omersiar]

Looks good for me, thanks.