[crossfire] [RFC] cfpython: raise minimum required version to Python 2.7

[Tolga Dalman]

Hi,

currently, Python 2.4 is required for the map scripts to work properly. I
propose to require version 2.7 as minimum Python version, which was released
in 2010 and is still widely used.

With Python 2.7, we have the opportunity to cleanup some very old Python
conditional stuff. This way we should be able to replace cjson by the
Python standard library JSON implementation. What do you think ?

Best regards
Tolga Dalman