Log Message:
Update 1.5.0 -> 1.6.0

Changes since 1.5.0:

* Added support for new "append" command that adds more description
  text to an existing task.
* Added support for the "weekdays" recurrence, which means a task can
  recur five times a week, and not on weekends (thanks to Chris
  Pride).
* UTF8 text is now supported in task project names, tags and
  descriptions.
* Fixed bug that caused the y/n confirmation on task deletion to
  ignore the Enter key and fail to re-prompt (thanks to Bruce
  Dillahunty).
* When the "echo.command" configuration variable is set to \ 
"yes", it
  causes commands that modify tasks to display which task was affected
  (thanks to Bruce Dillahunty).
* A task can now be annotated with the command "task annotate ...",
  and a timestamped annotation will appear in reports.
* A 'description_only' column is now available for use in custom
  reports, and it excludes annotations.
* A task can now be upgraded to a recurring task by adding a
  recurrence frequency, a due date, and an optional until date.
* When a recurring task is modified, all other instances of the
  recurring task are also modified.
* Custom reports now support user-specified column labels (thanks to
  T. Charles Yun).
* Task can now import tasks from a variety of data formats, including
  task export files from versions 1.4.3 and earlier, versions 1.5.0
  and later, todo.sh 2.x, CSV, plain text and task command line. See
  online docs for full details.
* Export was including 'id' in the column header even though it was
  not included in the data.
* The task file format has changed slightly. Please back up your task
  data files before upgrading to 1.6.0.
* Added new column 'recurrence_indicator' that displays an 'R' if the
  task is a recurring task. This column can be added to any custom
  report.
* Added new column 'tag_indicator' that displays a '+' if the task has
  any tags. This column can be added to any custom report.
* Fixed bug where sometimes a task description was concatenated oddly
  if there was a colon somewhere in the description.
* Fixed bug that caused recurring annual tasks to exhibit a creeping
  due date, because of an assumption of 365 days per year, which
  failed to consider leap years (thanks to T. Charles Yun).
* Annotations can now be modified with the substitution commands
  /from/to/.
* Substitutions can now be made global with /from/to/g and all
  occurrences of "from" will be replaced with "to".