Cleanup: Move private functions into its own source and header files

Cleanup: Move private functions into its own source and header files

It has become painfully apparent that much of the firewall main function needs to be broken down into smaller functions for managability and readability purposes.
The first step in doing such is to create a privte header and source files and move all internal functions there.
Everything in the private-* files are intended to never be exposed in the library.
Its only purpose is to make programming large projects more managable and readable.
As such, none of the functions should ever be considered part of the libraries/programs api.