* Handle graceful shutdown with unwinding
* Fix a race condition
* Avoid double exit deadlock
* typo: fix docs
* Fix ethkey cli compilation
* Fix all other cases panic_hook::set -> panic_hook::set_abort
* struct fields do not need to be public
* Add comments on why exiting AtomicBool is needed
* Update `add_license` script
* run script
* add `remove duplicate lines script` and run it
* Revert changes `English spaces`
* strip whitespaces
* Revert `GPL` in files with `apache/mit license`
* don't append `gpl license` in files with other lic
* Don't append `gpl header` in files with other lic.
* re-ran script
* include c and cpp files too
* remove duplicate header
* rebase nit
