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/ui/elements/reader_menu_order.lua

@@ -188,7 +188,7 @@ local order = {
     search = {
         "dictionary_lookup",
         "dictionary_lookup_history",
-        "vocabulary_builder",
+        "vocabbuilder",
         "dictionary_settings",
         "----------------------------",
         "wikipedia_lookup",