Add Ensenso support

If you want to test please read [the tutorial](https://github.com/VictorLamoine/pcl/blob/ensenso/doc/tutorials/content/ensenso_cameras.rst) first. For the last steps you will, of course, need an Ensenso device!

- The Ensenso grabber has been written like the OpenNI grabber class
- The code contains 2 examples, with/without the Ensenso grabber class
- The code is documented
- Support for Windows has not been tested
- A tutorial has been written to explain how to use the Ensenso in PCL

[pcl-developers topic](http://www.pcl-developers.org/IDS-Imaging-Ensenso-td5709495.html)
Remove `\n` completely. The user will add line breaks if he needs them. Also if the exception is not caught, it will be printed properly. Consider this sample:

```cpp
#include <stdexcept>
int main()
{
   throw std::runtime_error("We have a problem");
}
```

When run in terminal:

    $ ./demo 
    terminate called after throwing an instance of 'std::runtime_error'
      what():  We have a problem
    Aborted (core dumped)
    $