Discard UI library in favor of a ready set of components

[jonasraoni]

Discussion

The UI library isn't small (the ui-library/stable-3_5_0 has currently 991 files in 151 folders, with around ~16MB), and has its maintenance burden, there are package dependencies, the components need to be accessible, the design should be updated from times to times, everything needs to be upgraded, tested, fixed, documented, and modernized.

Therefore, following the same idea of adopting Laravel (maintenance delegated to a 3rd-party, bigger community, easier to find someone that has experience with the code, etc), I think it makes sense to use a 3rd-party library for our UI components, and build whatever we need around it.

Notice our UI library isn't composed just of UI components (550 files on the components folder). There are also "custom forms", helpers, etc, which we probably won't be able to delegate.

Some UI libraries out there offer different themes, which could be a bonus for the user (e.g. switch to a theme with higher contrast on the administrative panel).

Possible incompatibilities/lack of features can be fixed with PRs against the 3rd-party library.