Completely re-write base64 logic, make API suck less in doing so

src/engine/hint.cpp

@@ -18,13 +18,13 @@ bool Hint::IsValid(const util::Coordinate new_input_coordinates,
            facade.GetCheckSum() == data_checksum;
 }
 
-std::string Hint::ToBase64() const { return encodeBase64(*this); }
+std::string Hint::ToBase64() const { return encodeBase64Bytewise(*this); }
 
 Hint Hint::FromBase64(const std::string &base64Hint)
 {
     BOOST_ASSERT_MSG(base64Hint.size() == ENCODED_HINT_SIZE, "Hint has invalid size");
 
-    return decodeBase64<Hint>(base64Hint);
+    return decodeBase64Bytewise<Hint>(base64Hint);
 }
 }
 }