sexycat: eliminate gloval variables

This is the first step of making it a library.
sexycat: main() refurnishment

  * default $Opt_verbosity is set by main().  When we'll function
    as a library it's important to remain silent.
  * informational messages that used to go to stdout are output
    on $Info, which defaults to be stdout.  The driving reason
    for the change is not to clobber stdout when we dump a remote
    target on stdout.
  * is_file => is_local, so we use "local" consistently
  * init_endpoint() no longer called for local targets; its work
    is carried out by main() now
  * "disk-dumper" => "disk dumper"
  * bug fixes with regards to local input/output
sexycat: add -pP and -bB options

  * to control the rate of progress reporting
    -- disabled by default
    -- replaces the verbosity-based reporting
  * to control Opt_min_output_batch and Opt_max_output_queue
    -- I can't remember why they weren't tunable
sexycat: add user documentation

  * add the -h flag
  * if none of -sSdD is specified print usage information and exit
  * some developer documentation is added too
  * scsi_block_addr_t and scsi_block_count_t are changed to unsigned int
    from long, because we can't take advantage of 64bit yet
  * commented out code and data for output_st::granuality and ::optimum,
    because we don't make use of them yet
  * dropped the "source/destination is local" message