migrate to use of IdleConf and config files to set options

migrate to use of IdleConf and config files to set options

idle.py:
    Load the config files before anything else happens
    XXX Need to define standard way to get files relative to the
       IDLE install dir

PyShell.py:
ColorDelegator.py:
    Get color defns out of IdleConf instead of IdlePrefs

EditorWindow.py:
    Replace hard-coded font & window size with config options
    Get extension names via IdleConf.getextensions

extend.py:
   Obsolete.  Extensions defined in config file.

ParenMatch.py:
   Use config file for extension options.
   Revise comment about parser requirements.
   Simplify logic on find returning None.