* Refactor `TouchHandler` to handle double-tap and swipe gestures.
* Renamed existing `onTouch` JavaScript methods to `onItemTouch` and
added `onContentTouch` methods for swipe gesture.
* Refactor double-tap. It's now a method in `TouchHandler` versus
anonymous functions in `listen()` method.
* Updated CSS classes.
* Added `touch-action` CSS for `.entry-content`.
* Renamed CSS classes for adding events in `TouchHandler`.
* Updated users settings to replace checkbox for double tap with select
for none, double tap, or swipe.
* Added database migrations for new gesture_nav option.
* Rename `users.double_tap` to `users.gesture_nav` and migrate
existing user settings.
* Updated translation files. (Non-English updated with Google
Translate.)
Resolves#1449, closes#1495
Currently there is "Toggle read/unread = m", which toggles and
then goes to the next item.
Having the opposite operation available is handy, especially when adding
new feeds and going through them from oldest to newest posts.
It seems natural to map 'M' (= shift + 'm') for this action.
Closes https://github.com/miniflux/v2/issues/1352