test: link with boost_system
issue #175
io test: minors changes
add verbosity levels (available also for python binding)
minor change in Preload, default not using cache
nothing: adding verbose error messages
Merge branch 'develop' of github.com:tuttleofx/TuttleOFX into develop
Merge branch 'develop' of github.com:tuttleofx/TuttleOFX into develop