Merge branch 'extras' into new_extras

* extras: (42 commits)
  tests: adding testshell.sh and porting old testsuite.txt
  Bugfix: support commands combination for TODOTXT_SORT_COMMAND
  addon "add": fix incompatibility with OS X, thanks Dave!
  tests: Make test writing simpler and add two new tests.
  Bugfix: pri accepted priorities of more than a single letter
  Tests: new awk script to generate test scripts from session snapshots
  Cleanup: removing annoying trailing space on pri tasks
  Cleanup: del/depri/pri: some more $2 -> $item
  Bugfix: handling of priorities in pri/depri/do: no more globbing
  TODO_ACTIONS_D is now TODO_ACTIONS_DIR
  Parametrize .todo.actions.d location
  todo.actions.d: replace symlinks by short scripts
  Remove experimental alias support
  Remove experimental alias support
  Add support for aliases
  tests: first unset TODOTXT_CFG_FILE
  No need to source todo.cfg since it exports its vars
  Simple edit wrapper command
  nav: Made the URL regexp more flexible.
  nav: Added support for OS X using open.
  ...