groupid to handle dimmer arguments

[Stupco]

Is your feature request related to a problem? Please describe.
No

Describe the solution you'd like
Currently, groupid is for simple commands (which I get). However, it only works well for simple relays. Requesting it to provide ability to handle an additional parameter to handle brightness.

As @fvanroie states:
"it's not how groups work though...
the state is based on an event
which is represented as a percentage
on/off is 0%/100%
there is not inbetween"

Describe alternatives you've considered
There is no alternative for local brightness control without having to resort to HA.
However, restoring the previous brightness as mentioned #99 might solve the urgent need for this.

[fvanroie]

You can have a btnmatrix or a slider to control the L8-HD brightness. Object with a range of values can control the brightness proportional to their current value.

On/off controls like toggle buttons, switches and checkboxes only send 0% or 100% values.

[Stupco]

Workaround fixed with commit 75c8766

However, this creates a new issue: #212