Build system updates

This MR improves the overall build system configuration and adds a simple test configuration.

• App executables are now part of the default target and depend on the generation target.
• Raise minimum required CMake version to v3.16, resolving #6 (closed).
• Add executing experiments at experiments/hansbo_reproduction as system tests, see #2.
• List Python sources explicitly, resolving #5 (closed).
• Remove spurious global filesystem library link.