editconfig action module

Called from editconfig PIE screen by an authorised superuser, edits the PIE
configuration file

action routine

Input: CGI data from UIG (including userid, itemid, pageid, createnewlist)
Output: None

PDL

Get existing information from config file as config
Foreach CGI parameter
    Substitute this parameter's entry for existing entry in config
Overwrite existing config file with contents of config
Return editconfig page by printing an HTTP location (I don't think this is
necessay - I could just set the response parameter and return...)
Exit