fixes & enhandcements

(benchmark code..) implemented
repl completion very first version
(string xx) added
some builtin renames
a bit of comments
a bit of cocumentation
(sleep interval) added

ml_date.cpp

@@ -33,7 +33,7 @@ int string_to_date(const std::string &datestr, const std::string &format) {
 }
 
 int add_to_date(const int datetime, const int quantity, const std::string &part) {
-	// part is one of 'year', 'month', 'day', 'hour', 'minute', 'second', or 'millisecond'
+	// part is one of 'year', 'month', 'day', 'hour', 'minute' or 'second'
 
 	// very basic implementation, just for now - no timezones DST etc
 	time_t base = datetime;