build the struct of new impl which use db
Finished the DBImpl of Tracker, tests left to be done.
Use only one sql to do the request clients job
Move all Tracker stuff into the "Tracker" independent dir
Add CMakeLists.txt for the whole project. move proto dir to the root source dir to share the proto files.
add build/ rule to .gitignore, change project_name in CmakeLists.txt
Move netpack and error_code to public directory and change this two into shared libs
move README.md to the root dir, add remove_file_owner_info in TrackerDBManager.
modify all CMakeLists.txt files, use global variables to decouple
move README.md to the root dir
fix the root CMakeLists.txt that it doesn't recompile the proto files
Merge branch 'DBImpl' of github.com:wang2191195/CoolDown into DBImpl
move main of client and tracker into seperate file main.cc