* Move the license file of pyarmor from the install path of pyarmor package to user home path `~/.pyarmor`
* Refine error messages so that the users could solve most of problems by the hints.
* Refine command `pack`, use hook `hook-pytransform.py` to add the runtime files.
* The command `pack` supports customized spec file, refer to
https://pyarmor.readthedocs.io/en/latest/advanced.html#bundle-obfuscated-scripts-with-customized-spec-file
* In runtime module `pytransform`, the functions may raise `Exception` instead of `PytransformError` in some cases.
* In command `register`, add option `--legency` to store `license.lic` in the traditional way
* Fix platform name issue: in some linux platforms the platform name may not be right