This commit fixes the download link in the activity feed on the
sidebar and the mention link on card description and comments
(replaced by a popup).
`eslint .` now passes without any error or warning.
Fixes#286
Replace the old (and broken) jshint + jscsrc by eslint and configure
it to support some of the ES6 features.
The command `eslint` currently has one error which is a bug that was
discovered by its static analysis and should be fixed (usage of a
dead object).
The UI and the internal APIs are still rough around the edges but the
feature is basically working. You can now select multiple cards and
move them together or (un|)assign them a label.
The new EscapeActions object decide what to do when the user press the
Escape key (such as closing a opened popup or inlined form).
This commit also re-introduced the sidebar current view as a sidebar
component local state.
