related to #234 and #235, CMake "improvements"

  - moved some options (e.g., PDAL_BUILD_STATIC) to pdal_options.cmake
  - created (really borrowed from PCL) macros for adding libraries and
    executables: PDAL_ADD_LIBRARY, PDAL_ADD_EXECUTABLE
  - library linkage (i.e., PUBLIC/PRIVATE) determined at the top level
    in pdal_options.cmake
  - embedded boost lib name does not need quotes, in fact, we lose the
    correct path on Windows if they're there
  - install commands (mostly) moved inside the PDAL_ADD_* macros
tests don't fail locally, perhaps this has something to do with the unit
tests being installed, or linked with boost libraries multiple times,
let's try without the macro
if (NOT PDAL_BUILD_STATIC) seemed a little confusing; also seeing if the boost linkage is the problem with the build
linking PDAL_UTILITY against Boost appears to have been the source of all the havoc
Merge pull request #237 from PDAL/tweaking-cmake-files

proposed CMake modifications