Widespread CMake updates

Remove `FindCairo.cmake` and `FindFlann.cmake`, which are unused.

Include `FeatureSummary` which allows us to summarize package
information (found vs. not-found, required vs. optional, etc.) using
`set_package_properties` as well as optional features using
`add_feature_info`.

Add `set_package_properties` for each of our `find_package`
dependencies.

Add `add_feature_info` for each of our project `options`.

Turn on global property `USE_FOLDERS`, which cleans cleans up the MSVC
IDE quite a bit (filters, tests, etc. are grouped into project folders).

Remove `PDAL_LINKAGE` and `BOOST_LINKAGE`.

Find all packages in `QUIET` mode. We will still get error messages when
a package is not found, but success messages can be delayed until the
end of the master CMakeLists when `feature_summary` summarizes the
configuration for us.
Merge pull request #671 from PDAL/cmake-tweaks

Widespread CMake updates