Improve toggling between static/dynamic linking of dependency libraries

Follow-up to discussions in #2084.

Plan:

1. Remove options

• PCL_BUILD_WITH_BOOST_DYNAMIC_LINKING_WIN32
• PCL_BUILD_WITH_FLANN_DYNAMIC_LINKING_WIN32

2. Introduce options
   • BOOST_USE_STATIC
   • FLANN_USE_STATIC
   • QHULL_USE_STATIC

Open questions:

1. Do these options express strict requirement or just a preference? For example, if the user set FLANN_USE_STATIC=TRUE, but only dynamic libraries are available, is this a configuration error? Or do we issue a warning and coerce the option to FALSE?
2. How do these options interact with PCL_SHARED_LIBS? If shared libs are disabled, i.e. the user wants to compile PCL as a static library, should it force all the dependencies to be static as well?
3. Default values? Depending on the platform?

The second question may involve some complicated logic. Stepping a bit back, I wonder if such level of configurability is actually needed? Maybe PCL_SHARED_LIBS is sufficient? If it is set, then we default to finding shared dependencies and fall back to static. If it is not set, then we default to static and fall back to shared (or even error)?