Fix some of the Javascript linting issues, as well as bugs and unneeded divergences with upstream (#2208)

* Run eslint --fix

* Fix linting issues in video player and reduce divergences with upstream

This includes a behavior change of not auto-looping videos anymore. I don't
remember loops being ever intended, and they have been removed from upstream
a while ago, but we somehow missed the change.

* Fix lint issues in `app/javascript/flavours/glitch/selectors/index.js`

Those were basically caused by dead code that isn't present upstream, so
that brings us closer to upstream as well.

* Fix linting issue and bug in streaming/index.js

* Fix linting issues in config/webpack/shared.js

* Fix unused import in flavours/glitch/features/ui/index.js

* Fix linting issues and reduce divergences from upstream in flavours/glitch/features/ui/components/video_modal.jsx

* Fix linting issues in flavours/glitch/reducers

* Fix linting issues in glitch-soc onboarding modal

* Fix linting issues in flavours/glitch/features/ui/components/navigation_panel.jsx

* Remove dead code for unused local setting navbar_under

* Fix various linting issues

* Fix linting issues in flavours/glitch/components/scrollable_list.jsx and reduce divergences with upstream

app/javascript/flavours/glitch/features/compose/components/options.jsx

@@ -3,7 +3,6 @@ import PropTypes from 'prop-types';
 import React from 'react';
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import { defineMessages, injectIntl } from 'react-intl';
-import spring from 'react-motion/lib/spring';
 import Toggle from 'react-toggle';
 import { connect } from 'react-redux';
 
@@ -16,7 +15,6 @@ import LanguageDropdown from '../containers/language_dropdown_container';
 import ImmutablePureComponent from 'react-immutable-pure-component';
 
 //  Utils.
-import Motion from '../../ui/util/optional_motion';
 import { pollLimits } from 'flavours/glitch/initial_state';
 
 //  Messages.
@@ -125,7 +123,6 @@ class ComposerOptions extends ImmutablePureComponent {
     advancedOptions: ImmutablePropTypes.map,
     disabled: PropTypes.bool,
     allowMedia: PropTypes.bool,
-    hasMedia: PropTypes.bool,
     allowPoll: PropTypes.bool,
     hasPoll: PropTypes.bool,
     intl: PropTypes.object.isRequired,
@@ -190,7 +187,6 @@ class ComposerOptions extends ImmutablePureComponent {
       contentType,
       disabled,
       allowMedia,
-      hasMedia,
       allowPoll,
       hasPoll,
       onChangeAdvancedOption,