enhances auto3dseg data analyzer info

[wyli]

Description

• output file name extension to be consistent with self.fmt
• improve logging messages when writing files
• export file format may be spelt as 'yml' instead of 'yaml'

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests --disttests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.

[mingxin-zheng]

Thanks @wyli . It looks good to me.

[wyli]

/integration-test
/build