Added 403 and 404 error handling and error display on channels and notifications

src/channels/actions/EditChannelById.js

src/channels/actions/GetChannelById.js

src/channels/actions/GetPublicChannelById.js

...s/components/EditChannelComponent/EditChannelComponent.js

src/channels/pages/EditChannelPage/EditChannelPage.js

src/channels/reducers/Channel.js

src/channels/reducers/ChannelsList.js

src/common/pages/MainPage/MainPage.js

src/middleware.js

...otifications/pages/NotificationsPage/NotificationsPage.js

src/utils/error-component.js