Hyphenation: add custom hyphenation rules (#7746)

The hyphenation of a word can be changed from its default
by long pressing for 3 seconds and selecting 'Hyphenate'.
These overrides are stored in a per-language file, i.e:
koreader/settings/user-German.hyph.

frontend/apps/reader/modules/readerdictionary.lua

@@ -800,7 +800,7 @@ function ReaderDictionary:startSdcv(word, dict_names, fuzzy_search)
         -- dummy results
         final_results = {
             {
-                dict = _("Not available"),
+                dict = "",
                 word = word,
                 definition = lookup_cancelled and _("Dictionary lookup interrupted.") or _("No results."),
                 no_result = true,
@@ -849,22 +849,6 @@ function ReaderDictionary:stardictLookup(word, dict_names, fuzzy_search, box, li
         return
     end
 
-    -- If the user disabled all the dictionaries, go away.
-    if dict_names and #dict_names == 0 then
-        -- Dummy result
-        local nope = {
-            {
-                dict = _("Not available"),
-                word = word,
-                definition = _("There are no enabled dictionaries.\nPlease check the 'Dictionary settings' menu."),
-                no_result = true,
-                lookup_cancelled = false,
-            }
-        }
-        self:showDict(word, nope, box, link)
-        return
-    end
-
     self:showLookupInfo(word, self.lookup_msg_delay)
 
     self._lookup_start_tv = UIManager:getTime()