[SEMANAGE]: Added help text and spell check

Added the remaning help text except for --extract since I'm not sure what it
does. Also spell checked the existing text.
[LOGIN]: Added function handlers and login implementation

Added function handlers for each subcommand type with a print stub for most.
Then implemented the login handler. Also fixed bug in the noheader flag and
made sure that the login subcommand behavior was the same as the original
command.