Update help functionality:
    
        - Rename OPTIONNAM and OPTIONVAL variable names to ACTIONNAM and
          ACTIONVAL respectively.
    
        - Add positional parameters interpretation using getopt(1) inside
          help_searchIndex.sh function.
    
        - Rename REGEX to SEARCH inside help_searchIndex.sh. In this
          function the regex variable doesn't contain a regular expression
          but a search string so using `search' as name for the variable
          that holds it, seems to be more appropriate.
    
        - Update comments.