Change places adding '-' to testname output.

The '-' included in testname output was added at _bshtap_test_ok_ng,
but some features(e.g. skip) require to suppress '-' from their output.
This commit moves the places adding '-' to the output from
_bshtap_test_ok_ng to _bshtap_test_ok/_bshtap_test_ng.

It is to prepare adding 'skip' feature.
Add a wrapper function for cmp_ok
Add new feature 'skip'
Add documentation about skip
Add a new feature todo
Add documentation about todo
Merge branch 'skip-and-todo' into pu

* skip-and-todo:
  Add documentation about todo
  Add a new feature todo
  Add documentation about skip
  Add new feature 'skip'
  Add a wrapper function for cmp_ok
  Change places adding '-' to testname output.