pylib: generator: refactoring of some functions
commands: drop 20 line of code thanks to code refactoring

using Generator.generate_config_script I can drop 20 line of code
from this files
pylib: generator: now supports the new tag <configure>

configure is now the new holder for all pre/post and reconfigure tags
configure has now a phase tag which can be used to specify in
which phase the code should be used for the moment pre,post
are for kickstart and reconfigure is for reconfiguring.

There is still more testing and code refactoring that must be done