re-structure gateway devices

[starkillerOG]

Restructure the gateway devices to put everything with simular API together.
The next step is to use common classes for devices with simular API (to be done in this PR).

This PR also creates the base classes for switches and light bulbs, so all known models are now fully supported, although some models have not been tested (they are assummed to have simular API calls as devices that are closely related).

This PR also adds subdevice support for the lumi.gateway.mgl03 and is a first step towards subdevice support for the lumi.gateway.mieu01

[coveralls]

Coverage decreased (-6.2%) to 67.721% when pulling 3b3a3c9 on starkillerOG:patch-17 into 93b7a77 on rytilahti:master.

[starkillerOG]

@rytilahti could you look if you agree with this structure for the gateway devices?
We have discussed this re-structuring before.

[starkillerOG]

@rytilahti This is now finished, all tests pass and it now also includes all base classes for switches and light bulbs.

I can not actually test is since I don't own switches or light bulbs, but I am pretty sure it will work.
It is tested and does work with the weather sensors.

If this gets merged I can add all the light bulbs and switches to HomeAssistant.

[starkillerOG]

The use of python-miio (importing) does not change with this PR, the following script will still work as it used to:

from miio import Gateway

gateway = Gateway("192.168.1.IP", "TokenTokenToken")

gateway.discover_devices()
devices = gateway.devices

for dev in devices.values():
    try:
        dev.update()
    except Exception as ex:
        print("got exception during update for %s: %s" % (dev.device_type, ex))
    print(dev)

[rytilahti]

Hey, sorry for taking the time, it's a huuuge diff and I haven't found time to look much into it until now. Here's my initial round of comments, more will follow up later after the first round of changes :-)

[starkillerOG]

@rytilahti no problem, you don't have to hurry, it is indeed a large restructure.

I won't have any time the next 3 weeks since I will be moving to a new house.
So I don't know if I will be able to finish this PR any time soon, but maybe in the evening hours.... we will see.

[starkillerOG]

@rytilahti I have prosessed all feedback and all tests pass again.

[MicroSur]

Is this PR will bring Aqara relay support in HomeAssistant at last?

And is it possible to expect the function of displaying the power consumtion on xiaomi wall switch with neutral line?

[starkillerOG]

@MicroSur yes and yes.
But I will not have time to work on it in the coming weeks, and it still needs a second revieuw

[starkillerOG]

Whoops, I messed up the re-base to fix some merge conflicts.
Therefore I will close this PR and make a new one here: #924