[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/readerdogear.lua

@@ -1,3 +1,4 @@
+local BD = require("ui/bidi")
 local Device = require("device")
 local Geom = require("ui/geometry")
 local ImageWidget = require("ui/widget/imagewidget")
@@ -33,6 +34,7 @@ function ReaderDogear:setupDogear(new_dogear_size)
             dimen = Geom:new{w = Screen:getWidth(), h = self.dogear_size},
             ImageWidget:new{
                 file = "resources/icons/dogear.png",
+                rotation_angle = BD.mirroredUILayout() and 90 or 0,
                 width = self.dogear_size,
                 height = self.dogear_size,
             }