[RTL UI] update widgets and apps for UI mirroring

Small tweaks all around to handle UI mirroring:
- swap existing symbols like arrows, or use alternative ones
- rotate some images, like chevrons and dogear icons
- flip some left and right swipe handling
- flip some geometry arithmetic like tap on left or right
  side of page or dict window
- use new ProgressWidget:getPercentageFromPosition() instead
  of geometry arithmetic
- BD.wrap() some concatenated string bits, like in reader
  and menu footers
- flip inverse_reading_order when UI is mirrored

More specific tweaks:
- ReaderGesture: reset some specific gestures when UI direction
  has changed (tap on top/bottom left/right corners, for
  bookmarks and FileManager "Plus menu").
- ReaderRolling: show markers on the correct side of page,
  in single or dual page mode.
- KoptOptions: swap left and right icons in Alignment toggle
- CheckMark: proper rendering in all 4 mirroring/rtl combinations.
- VirtualKeyboard: forbid any mirroring
- Move util.getMenuText into Menu.lua

frontend/apps/reader/modules/readerbookmark.lua

@@ -1,3 +1,4 @@
+local BD = require("ui/bidi")
 local CenterContainer = require("ui/widget/container/centercontainer")
 local ConfirmBox = require("ui/widget/confirmbox")
 local Device = require("device")
@@ -231,7 +232,7 @@ function ReaderBookmark:onShowBookmark()
                     w = Screen:getWidth(),
                     h = Screen:getHeight(),
                 },
-                direction = "east"
+                direction = BD.flipDirectionIfMirroredUILayout("east")
             }
         }
     }