Update Interactive ICP tutorial

Here is what has been done:
- Format code to match PCL style guide
- Switch from `floats` to `double` to improve precision (see [topic](http://www.pcl-users.org/Pcl-registration-Strange-td4035016.html)). There is a warning in the code to prevent people to use this for other purposes than demonstration
- Several minor improvements (typo in `printMatrix`, useless conditions, added `TicToc` timers)
- Updated `rst` file to match the new `cpp` file and updated titles format.
- Added a warning about precision in the `rst` file