improve build script
reclaim memory from the singleton class that won't delete its instance
Merge pull request #388 from haiwen/reclaim_memory_from_singleton

reclaim memory from the singleton class that won't delete its instance
Merge pull request #382 from haiwen/improve_build_script

improve build script
wait for seaf-daemon to quit and remove the related warnings
Merge pull request #387 from haiwen/remove_qprocess_warning

wait for seaf-daemon to quit and remove the related warnings
support multiple upload (backend part)
support multiple upload (ui part)
clean up code from returning shared_ptr directly