[RTL UI] use auto or LTR text direction in some specific cases

Allow TextBoxWidget new text direction/lang parameters to be
set on upper widgets, and propagate them all the way to it
(ScrollTextWidget, InputText, InputDialog, TextViewer).

Use specific non-default ones in some specific cases:
- Force LTR text direction when showing HTML and CSS, and
  configuration files (in some plugins).
- Use Wikipedia server language and text direction when
  showing an article.
- Use auto with Dictionary results, as we don't know the
  dictionary language, and they may contain mixed content.
- Force LTR when showing some paths (still needs more of them)

TextEditor plugin: add 2 new options "Auto paragraph direction"
and "Force paragraph direction LTR".

Footnotes popup: grab HTML direction, and forward it
to MuPDF for proper display.

frontend/apps/reader/modules/readerstyletweak.lua

@@ -97,6 +97,7 @@ function TweakInfoWidget:init()
             text = css,
             face = Font:getFace("infont", 16),
             width = self.width - 2*Size.padding.large,
+            para_direction_rtl = false, -- LTR
         }
     })
     if self.is_global_default then