Wrote new method note_list::find_note_id

New method will search all notes and return the note's id/index in the
note_list instance. This will help prevent duplication of code as well as
provide a sort of "note_exists" functionality.

Replaced other iterrators that were used for checking for a note's existance
(note_list::edit and note_list::cat) with calls to this.
Added default edit behavior with only note name

Now when a user just specifies "noteless note_name", the note will
automatically be opened for edit without having to specify the edit command.

This commit though needs some follow up work done to clean up some badly
written main level functions.
Modified most main-called functions to return int

With the new default of edit if a command doesn't match but a note with that
name exists, noteless doesn't stop parsing arguments until it hits the end of
argv. Having all the of main-called functions return int allows it to return
status codes, thus exiting at the appropriate time with the added benefit of
being able to programatically work with most of these functions now.