Pyarmor

* 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

* Refine `pytransform` to handle error message of core library
* Refine command online help message
* Sort the scripts being to obfuscated to fix some random errors (143)
* Raise exception other than call `sys.exit` if `pyarmor` is called from another Python script directly
* In the function `get_license_info` of module `pytransform`
- Change the value to `None` if there is no corresponding information
- Change the key name `expired` to upper case `EXPIRED`