Merge branch 'actuator_line' of https://git.rz.tu-bs.de/irmb/uppsala/VirtualFluids_dev into actuator_line

Merge branch 'actuator_line' of https://git.rz.tu-bs.de/irmb/uppsala/VirtualFluids_dev into actuator_line

Clean up grid generator

See merge request irmb/VirtualFluids_dev!72

Make boost optional for all user. When BUILD_USE_BOOST is enabled cmake will...

See merge request irmb/VirtualFluids_dev!71

Make boost optional for all user. When BUILD_USE_BOOST is enabled cmake will look for the boost header only libraries. Afterwards boost needs to be linked to the required library.
e.g:
if(BUILD_USE_BOOST)
    target_link_libraries(${library_name} PRIVATE Boost::boost)
endif()

Adding SPDLOG dependency (closes #19)

Closes #19

See merge request irmb/VirtualFluids_dev!69

Add build cache cmake function. Use ccache if available. Therefore removed...

See merge request irmb/VirtualFluids_dev!68