Vocabulary builder: store word context, other tweaks and fixes (#9195)

Add a copy button and save word context (off by default), shown
via the three-dot menu of word entries.
Also some db refactoring and minor UI improvements:
- a dedicated book title table in order to shrink db size by storing
  references to title names instead of repeated actual strings,
- alignment of different forms of the "more" button and possible
 clipped words in translations.
- fix plugin name so it can be disabled

frontend/apps/reader/modules/readerdictionary.lua

@@ -888,13 +888,13 @@ function ReaderDictionary:stardictLookup(word, dict_names, fuzzy_search, boxes,
         return
     end
 
-        local book_title = self.ui.doc_settings and self.ui.doc_settings:readSetting("doc_props").title or _("Dictionary lookup")
-        if book_title == "" then -- no or empty metadata title
-            if self.ui.document and self.ui.document.file then
-                local directory, filename = util.splitFilePathName(self.ui.document.file) -- luacheck: no unused
-                book_title = util.splitFileNameSuffix(filename)
-            end
+    local book_title = self.ui.doc_settings and self.ui.doc_settings:readSetting("doc_props").title or _("Dictionary lookup")
+    if book_title == "" then -- no or empty metadata title
+        if self.ui.document and self.ui.document.file then
+            local directory, filename = util.splitFilePathName(self.ui.document.file) -- luacheck: no unused
+            book_title = util.splitFileNameSuffix(filename)
         end
+    end
 
     -- Event for plugin to catch lookup with book title
     self.ui:handleEvent(Event:new("WordLookedUp", word, book_title))