[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/readermenu.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")
@@ -373,10 +374,10 @@ function ReaderMenu:_getTabIndexFromLocation(ges)
         return self.last_tab_index
     -- if the start position is far right
     elseif ges.pos.x > 2 * Screen:getWidth() / 3 then
-        return #self.tab_item_table
+        return BD.mirroredUILayout() and 1 or #self.tab_item_table
     -- if the start position is far left
     elseif ges.pos.x < Screen:getWidth() / 3 then
-        return 1
+        return BD.mirroredUILayout() and #self.tab_item_table or 1
     -- if center return the last index
     else
         return self.last_tab_index