Update eslint to v5, and eslint related plugins

[daniel-wer]

Issues:

• Circular class dependencies due to flow types (Support cyclic type declarations (#485) babel/babel-eslint#584)
• eslint-config-airbnb eslint v5 support (eslint v5 support airbnb/javascript#1834)
• button-has-type false positive - wait till Account for pragma in button-has-type jsx-eslint/eslint-plugin-react#1851 is released

[daniel-wer]

After updating eslint-config-airbnb we need to discuss whether to tweak/disable some of the new rules. @philippotto @normanrz What do you think? :)

• import/order Could be fixed automatically according to the docs. Imo this could be helpful.
• import/no-cycle I don't really see us fixing that.
• react/destructuring-assignment I disabled it for now as this caused a loooot (> 500) of errors. (every time this.props.<anything> was used in any react component render method...)
• react/no-access-state-in-setstate Around 50 errors.
• lines-between-class-members Reasonable with the "exceptAfterSingleLine": true option imo (for declaring instance variables without a newline). Unfortunately, this errors if a flow type definition causes an instance variable declaration to have multiple lines :(
  For example eslint wants a newline after the dataLayers line in this example:

connectionInfo: ConnectionInfo;
dataLayers: {
  [key: string]: DataLayer,
};
isMappingSupported: boolean = true;
maximumDataTextureCountForLayer: number;

If you want to have a look at the linting errors yourself, check out the update-eslint branch and run yarn lint.

[normanrz]

I don't have a strong opinion on the stylistic rules.
react/no-access-state-in-setstate I think might be worthwhile fixing for future proofing. Not sure if feasible everywhere.

[philippotto]

import/order Could be fixed automatically according to the docs. Imo this could be helpful.

Nice 👍

import/no-cycle I don't really see us fixing that.
react/destructuring-assignment I disabled it for now as this caused a loooot (> 500) of errors. (every time this.props. was used in any react component render method...)

Agree.

react/no-access-state-in-setstate Around 50 errors.

I'd disable it for now and create a separate issue for it, so that it doesn't block the update in general. As @normanrz said, it's probably nice for future proofing.

lines-between-class-members Reasonable with the "exceptAfterSingleLine": true option imo (for declaring instance variables without a newline). Unfortunately, this errors if a flow type definition causes an instance variable declaration to have multiple lines :(
For example eslint wants a newline after the dataLayers line in this example: [...]

Let's ignore that for now, since it brings new problems.