The "edit settings" dialog should not change the config file from relative to absolute paths

Solve the issue addressed in https://groups.google.com/forum/#!topic/civetweb/nLWFbVLZXAg: The "edit settings" dialog did change the config file from relative to absolute paths.

This patch allows to load the configuration
a) from a file
b) from the currently running civetweb instance
c) from the definition of defaults

This patch is not the one by Tony Wilk - the problem has been solved differently, by extending the dialog and giving the user more options.

Tested in Win32.
Feature is not available for Linux, so it has only been tested that there are no side effects on Linux systems.