Add `get_zimId` method to Result

get_zimId method allows the user to get the uuid of the archive from
which a result is retrieved directly from the search result itself.

include/searcher.h

@@ -49,6 +49,7 @@ class Result
   virtual int get_wordCount() = 0;
   virtual int get_size() = 0;
   virtual int get_readerIndex() = 0;
+  virtual std::string get_zimId() = 0;
 };
 
 struct SearcherInternal;

src/searcher.cpp

@@ -46,6 +46,7 @@ class _Result : public Result
   virtual int get_wordCount();
   virtual int get_size();
   virtual int get_readerIndex();
+  virtual std::string get_zimId();
 
  private:
   zim::SearchResultSet::iterator iterator;
@@ -265,6 +266,12 @@ int _Result::get_readerIndex()
 {
   return iterator.getFileIndex();
 }
+std::string _Result::get_zimId()
+{
+  std::ostringstream s;
+  s << iterator.getZimId();
+  return s.str();
+}
 
 
 }