Use member instead of homegrown string=any?.

The built in procedure 'member' suits my needs for this purpose, making it unnecessary to define string=any?.
Handle 0 command line arguments properly.

Previously, running the executable without any command line arguments resulted in a crash. Now if no command line arguments are specified, a message will be printed prompting the user to type 'hog help' for a list of commands.
Added design notes on database schema.
Double spaced design notes.
Updated design notes to refer to Chicken Scheme.

Since this branch focuses on using Scheme for the implementation, the design notes have been changed to reflect that.