Remove TODOs about parsing/printing custom formats

It makes likely more sense to implement that entirely in user code. The
parsing/printing functions for common formats have also been improved so
this is likely not very relevant anymore anyways.

chrono/datetime.cpp

@@ -47,8 +47,6 @@ template <typename num1, typename num2, typename num3> constexpr bool inRangeExc
  *    the time zone deltas are "baked into" the DateTime instance. For instance, the expression (DateTime::now() - DateTime::gmtNow())
  *    returns one hour in Germany during winter time (and *not* zero although both instances represent the current time).
  * \todo
- * - Add method for parsing custom string formats.
- * - Add method for printing to custom string formats.
  * - Allow to determine the date part for each component at once to prevent multiple
  *   invocations of getDatePart().
  */

chrono/timespan.cpp

@@ -24,9 +24,6 @@ namespace CppUtilities {
  * and month. For that use case, use the Period class instead.
  *
  * \remarks Time values are measured in 100-nanosecond units called ticks.
- * \todo
- * - Add method for parsing custom string formats.
- * - Add method for printing to custom string formats.
  */
 
 /*!