Eslint formatting updates

[jacogr]

Added 2 rules, both where we have been making comments on PRs which could just be caught by eslint. (Applied auto-fixes and actually checked/adjusted in a couple of cases where fixes were done not quite 100%)

1. newline-after-var - eslint found us mostly consistent here, however around 320 auto-fixes applied. Always prefer

const foo = '123';
let bar;

if (xyz === foo) {
  return;
}

instead of

const foo = '123';
let bar;
if (xyz === foo) {
  return;
}

2. one-var-declaration-per-line - eslint found us 99.99% compliant, auto-fixes applied in 6 files. Always prefer

let foo = '123';
let bar;
let baz;

instead of

let foo = '123, bar, baz;

[ngotchac]

All right for me. Might want to wait for @derhuerst opinion