* MM-13209: fix textbox to bind channel from props

This avoids relying on a global notion of the current channel, which only applies to the centre and not the RHS.

* update mattermost-redux

* code review feedback

* update mattermost-redux

* MM-12233: supply local at mention results immediately

* temporary redux commit

* show special mentions after channel members

* fix edit channel header modal textbox interaction

* updated mattermost-redux commit

* address review feedback

* Removing SuggestionStore.

* Fixing clicking mention in popover.

* Fixing laggy text manipulation.

* Feedback fixes

* Add interactive menus to message attachments

* Updating styling for attachment dropdown

* Updating input box changes

* Updates per feedback

* Updating styling for actions

* Updating pointer events for arrow icon

* Updating webhooks

* Updating css for mention list item

* Add ability to show a no results message in the suggestion box

* Update snapshots

* Add submitted message after a valid option is selected

* Updating UI for action messages

* Add view reducer for menu actions

* Updating feedback in RHS

* Update per feedback

* Close channel autocomplete if multiple tildes are typed

* Cancel dispatch on slower connections to prevent autocomplete re-opening

* MM-11291 Prevent duplicate channel autocomplete requests after user presses space

* Updated snapshots

* use Link in Textbox

Introduce react-router-enzyme-context to enable unit testing of same
with `mount` vs. `shallow`.

* leverage browserHistory in SystemUsersDropdown

Note that the demotion modal isn't actually being shown at present: the
transition of self from system admin to regular member is done without
confirmation after a partial refactor last year.

* leverage browserHistory in Authorize

* leverage Link in SignupController

* leverage browserHistory in UserSettingsSecurity

* extract base path from config's SiteURL on logout

* move __webpack_public_path__ into entry.js

This ensures that the other imports aren't hoisted above the definition.
Additionally re-export the public path back onto window.publicPath to
cover development environments.

* rely on window.basename in autolinkChannelMentions

While globals should generally be avoided, this is one of only two
places where `window.basename` is used. Moving it into the store and
rewriting the text rendering to pass down (or wrap) the necessary state
may be premature, given the pre-existing need for this variable to be
global.

* update getSiteURL to respect subpath

Additionally leverage getSiteURL over accessing window.* directly.

* strip any trailing slash before appending the ws pathname

* lint fixes

* use window.location.originw when SiteURL not defined

* Adding emoji after word limit is reached will give warning message.

* New test case added for textbox.js

* Show Unread Channels in Channel Selector when input is empty

* Display mention count. Order with the same sort as Unread on sidebar.

* Use getUser from redux. Change key name.

* fix for styles on Firefox that appear on next line.

* Re-evaluate character count on focus event

* make check-style

* Moved Utils.generateRandomString(...) into TestHelper.randomString(...)