Add Install and Uninstall targets

[JWhitleyAion]

This PR fills out all of the necessary CMake instrumentation to make this a stand-alone, installable (and un-installable) package with instructions like:

mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release -DBUILD_TESTING=0
make
sudo make install

This installs canard.h, canard/*.h, canard_tgt.a, and a few CMake files which make it possible to find_package(Canard) in another CMake project. Also:

sudo make uninstall

Will remove the package and associated files which were installed.