Rename + file restructuring

From now on this(emu) component will be named "rainforest". This reflects the name of the manufacturer instead of the model number. Which is how most official components are named (examples: Raincloud, Ring, etc.)

Some file structuring were also necessary to make the component continue to work with Home Assistant in the future (as outlined on the official developers blog).

Here are a list of changes:

• Reorganized the custom_components folder in the fashion required from now on. (example: emu2/sensor.py instead of sensors/emu2.py)
• Created init.py.
• Created manifest.json.
• Created custom_components.json (in the root of this repository).
• Renamed the emu2 to rainforest.