Start with the product selection

[dgdavid]

As proposed by @joseivanlopez in the context of #192, D-installer could start with a screen for selecting the product. It does not break the main idea of starting with the summary, but just adds a preliminary step that could help to avoid an extra (and undesired) probing.

I like the idea, which we can materialize with a screen using Cards or Tiles rendering the product name, its description and even its logo. Something like the screenshot below, but improved.

However, this challenge us to start thinking on a better navigation between screens.

Tasks

• Introduce react-router to have proper navigation.
• Do not read the repositories until the installation starts (no need, by now, to fetch information from there).
• If only one product is available, select such a product (by now, apply the same config to all services). If there are multiple products, do not make any proposal until one is selected.
• Display a product selection screen when no product is selected (multiple products are available).
• Reload the configuration when the user selects a different product (each service should listen for that signal).

[joseivanlopez]

Selecting a product supposes to reinitialize the installation: new probing, previous selections are lost, etc. Showing a first dialog with a presentation of all available products would have two benefits: it makes the installer more understandable and it makes more explicit an important selling point ("support for multiple products, versions or even distros").

The idea is to show all the products at first sight. Then, after selecting a product, we would directly land at the "Summary" dialog. Note that we could drop the probing dialog and the progress bar because the probing phase will be done in parallel once we will have multiple services. So, we could go right to the "Summary" using the "skeleton" technique to indicate that a section is being calculated. Moreover, I would use the name of the selected product as title for the dialog. Of course, the UI should still make possible to go back and change the product. Also note that the "Summary" dialog could be adapted to the selected product. For example, openSUSE distros would not have a registration module.