Use PROJECT_SOURCE/BINARY_DIR instead of CMAKE_SOURCE/BINARY_DIR

[SJ-Innovation]

When including this library using the FetchContent_* functionality of CMake the wrongly scoped directories are used, making the project fail to build & link correctly.

PR momentarily.

[abgandar]

Committed in #56

[abgandar]

Note that this also required #58 as an additional change to actually make FetchContent work. See updated Tutorials in dacelib/tutorials repository for example of how to use FetchContent.