[web] Stop exporting all components

[dgdavid]

TL;DR: rewrote namespace/index.js files for exporting only public components

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As discussed at #1045 (comment), right now we're exporting all components via their namespace's index.js file. However, as @joseivanlopez wrotes, it should export the pages and the components that might be reused from pages out of its namespace. The rest should be considered as internal components.

Instead of start diverging the way it is currently done in a single namespace, I've created this issue for addressing all of them at once.

[lslezak]

Note: exporting everything and using the internal components might cause dependency cycles which break hot module replacement. See related #1214 .