devel/py-robotremoteserver: Allow use Python 3.x

Remote server version 1.1 and newer support Python 2.6, 2.7, 3.3, and newer.
Remote server 1.0 series supports Python versions 2.2-2.7.

https://github.com/robotframework/PythonRemoteServer#id12

While here, add LICENSE_FILE.

PR: 223166
Approved by: vladimir.chukharev@gmail.com (maintainer)