Bug Fixes

Made the following changes:
1.) Consolidated error logging in the admin section
2.) Added a "memory tracer" internal debugging function, for tracing
memory leaks (disabled by default - only use if you suspect a memory
leak!)
3.) re-factored the way that request variables are handled, so that a
mixture of POST and GET can be used, rather than either/or. POST has
priority over GET
4.) Fixed a bug where topics were being ignored when searching for
matching AIML categories
5.) Corrected several "undefined index" bugs throughout the script
6.) Minor cosmetic changes to the debugger's output