Redesign and refactor

All the code has been refactored to match some simple rules. See DEV.md for more information about those rules, to be completed in the future to ensure solid contributing guidelines.
The features haven't changed except for the "custom icon" feature that has disappeared because it wasn't stable enough. I have some ideas about that and will submit a pull request at some point in the future to reimplement it.
The main architectural change is that favorite beers are now stored in a single localStorage variable (favoriteBeers) and respect the OSM brewery tag's principle: "beer1;beer2;beer3".
Also, files have been rearranged to separate 3rd party code from custom code. I have made some changes to these 3rd party files that I plan on suggesting upstream at some point (especially in OverPassLayer.js and osm-js-editor).
This is a work in progress and some french comments and names remain that should be changed in the future. But it's a start!
Other cases are nodes which are parts of a way, like house numbers or entrances. They should be ignored.