[ajax] refactor/cleanup low-level ajax functions
* loadxhtml/replacePageChunck/reload_component/reload_box deprecated in favor of loadXHTML / ajaxFuncArgs
* some other cleanups in cubicweb.ajax.js
* add js_render which will replace js_component (more generic, nicer argument passing handling)
from os.path import join
from cubicweb.toolsutils import create_dir
option_renamed('pyro-application-id', 'pyro-instance-id')
create_dir(join(config.appdatahome, 'backup'))