CMake improvements?

[Anton3]

In order to be able to use RansacLib as a modern CMake library, I had to:

1. Move RS_ROOT/RansacLib directory to RS_ROOT/include/RansacLib, because otherwise I'd get examples, LICENSE and README in the include directory
2. Delete CMakeLists.txt and write my own, which says:

project(RansacLib LANGUAGES CXX)
add_library(RansacLib INTERFACE)
target_include_directories(RansacLib INTERFACE RansacLib/include)
target_compile_features(RansacLib INTERFACE cxx_std_11)

What about including this "out of the box"? CmakeLists.txt could create the header-only CMake library by default, and build examples when passed some additional flag.

[tsattler]

Do you want to create a pull request for this? Would be happy to merge this in.