[core] Apply 3 different fixes

[oliviertassinari]

• PR has tests / docs demo, and is linted.
• Commit and PR titles begin with [ComponentName], and are in imperative form: "[Component] Fix leaky abstraction".
• Description explains the issue / use-case resolved, and auto-closes the related issue(s) (http://tr.im/vFqem).

I was trying to push some code into production with the master state.
I have come across those issues.

• Prevent using style conflicting properties like border and border Button
  Warn when using overlapping styles (e.g. border and borderBottom) facebook/react#6348
• Avoid using ES6 features that can't be transpiled with the runtime plugin like includes
• Remove dead style properties

Fix #5697