Use Javascript class syntax

[hiddewie]

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This PR

Cleans up the definition of backend classes massively, by using the Javascript class syntax. This allows:

• class A instead of .prototype
• constructor and super instead of static calls to parent prototypes.
• A extends B instead of util.extends(...)

[yohanboniface]

Thanks a lot for this work!
Can you also have a look at plugins that would inherit from core classes ? From the top of my head I can remember kosmtik-tiles-export and kosmtik-mbtiles-export at least.

Otherwise I'll have a look myself, but I'm a bit in a rush there days :(

[hiddewie]

@yohanboniface Thanks for reviewing + merging so quickly :)

Yes, definitely. It would be nice to also have the plugins up-to-date considering the code style. I will make some PRs in those plugin repos.

After that, it would be nice to have NPM releases to let users (also see #309) without intimate Javascript/NodeJS knowledge install the package using the instructions in the readme.

It would also be nice to have Travis build PRs / branches, such that feedback is available in Github PRs about the build status, before merging the PR.

[hiddewie]

@yohanboniface I went through the entire list of plugins, and updated the (backend) code to the class syntax whereever possible.

[yohanboniface]

Fantastic work, thanks!

[yohanboniface]

After that, it would be nice to have NPM releases to let users (also see #309) without intimate Javascript/NodeJS knowledge install the package using the instructions in the readme.

Sure! Missing time to do it right away, I'll try next week, same for Travis :s