DictQuickLookup: various tweaks

- Rework widget layout to avoid implicit (and wrong)
  sizing, using proper padding/margins and correct
  measurements of components.
- Adjust lookup word font size so it's not smaller
  than the definition.
- Tweak small window positionning: keep it centered
  if possible, only move it to keep the highlighted
  word shown when we can.
- Large window: adjust to screen size correctly,
  leaving room for footer.
- Always have a "Close" button at bottom right.
  Former always displayed button "Follow link" will
  be added as a 3rd row in the rare case we select
  a word in a link.
- Replace "tap on lookup word to edit and redo the
  query" with an icon on the right: tap on it to
  edit the queries word, long-press to edit the
  current result word. Only close the current dict
  window when lookup is launched.
- Remove feature "tap on title to set current dict
  as the default dict for this document", as it didn't
  really work, and it was bad UX.

frontend/apps/reader/modules/readerdictionary.lua

@@ -853,7 +853,6 @@ function ReaderDictionary:showDict(word, results, box, link)
             selected_link = link,
             results = results,
             dictionary = self.default_dictionary,
-            width = Screen:getWidth() - Screen:scaleBySize(80),
             word_box = box,
             -- differentiate between dict and wiki
             is_wiki = self.is_wiki,
@@ -1009,6 +1008,7 @@ function ReaderDictionary:downloadDictionary(dict, download_location, continue)
     end
 end
 
+--[[ No longer used
 function ReaderDictionary:onUpdateDefaultDict(dict)
     logger.dbg("make default dictionary:", dict)
     self.default_dictionary = dict
@@ -1019,6 +1019,7 @@ function ReaderDictionary:onUpdateDefaultDict(dict)
     })
     return true
 end
+]]--
 
 function ReaderDictionary:onReadSettings(config)
     self.default_dictionary = config:readSetting("default_dictionary")