* Improve the boost rule including user_options attribute.
Then --with-<library> parameter can be passed to build only that library
Modify examples to demonstrate how to use it.
However, building examples takes too long time, so do not include them into the tests.
* implements pcl cmake_external build rule
* Improve example with building PCL (Point Cloud Library):
- build boost library and use it as dependency
- add/correct some properties
* implements pcl cmake_external build rule
* Improve example with building PCL (Point Cloud Library):
- build boost library and use it as dependency
- add/correct some properties
