Default settings: Support common types of documentation comment and @todo tag

[slaugaus]

Adds @todo as a default tag and makes the default regex support comments starting with:

• /** (start of a Javadoc standard doc comment)
• * (start of a new line of a doc comment)
• /*! (Qt-style or important comment block)
• /// (C# and Doxygen)
• //! (Doxygen)
• """ (Python docstring)

Inspired by this page of the Doxygen docs.

Tested in RegExr: