[UX improvements] Steps to add a plant

[jpbaril]

Straight from the first step/page we are asked to select the sensor entities for the plant to be added but we have not yet queried and so received results and chosen the appropriate plant at that point. So, if we made a mistake in the plant species name or that no results are found then we need to close the window and start again the process of adding a plant.

The steps should be as follow:

1: Only ask the species name to search for.
2. Show result list.
3. From that result page we should be able to change the search string and resubmit for new results.
4. Selecting an item in results list should query and show the image.
5. Clicking "Next" should bring us to a page where we can input the plant's name and select the sensor entities for the plant. (Ideally we should also be able to click "Previous" to return to previous step)

[Olen]

The integration is created to be independent, not everyone uses openplantbook to search for species.
There are also some very limited possibilities when it comes to functionality (back/forward/retry etc. etc.) in the HA config-flow.
But please provide a PR, and I'll look into it.

[ChristophCaina]

I would add the following:

first step:

• Checkbox: Do you want to use OpenPlantBook -> Yes / No
  then, if yes -> ask for the species name
  if not -> directly assign sensors to the plant, without the openPlantBook request