Pyarmor

* 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

* Support new linux platform `centos6.x86_64`, arch is x86_64, glibc < 2.14
* Do not print traceback if no option `--debug` specified as running `pyarmor`

* When the obfuscated scripts raise exception, eliminate the very long line from traceback to make it clear

* Fix issue: `pyarmor` load `_pytransform.dll` failed by 32-bit Python in 64-bit Windows.

* Add option `--update` for command `download` to update all the downloaded dynamic libraries automatically
* Fix issue: the obfuscated script raises unexpected exception when the license is expired

* Standardize platform names, refer to
https://pyarmor.readthedocs.io/en/v5.7.5/platforms.html#standard-platform-names
* Run obfuscated scripts in multiple platforms, refer to
https://pyarmor.readthedocs.io/en/v5.7.5/advanced.html#running-obfuscated-scripts-in-multiple-platforms
* Downloaded dynamic library files by command `command` will be saved in the
`~/.pyarmor/platforms` other than the installed path of pyarmor package.
* Refine `platforms` folder structure according to new standard platform name
* In command `obfuscate`, `build`, `runtime`, specify the option `--platform`
multiple times, so that the obfuscated scripts could run in these platforms