Removing shar(1)

Hi,

I was reminded the other day that shar(1) exists, though it's use is no 
longer recommended in ports.  The same functionality can be found in 
tar(1) instead, so I think we should deorbit /usr/bin/shar and stop 
promoting it entirely.  sh(1) archives are really problematic from a 
user standpoint for at least one reason best explained by the manpage:

  It is easy to insert trojan horses into shar files.  It is strongly
  recommended that all shell archive files be examined before running
  them through sh(1).  Archives produced using this implementation of
  shar may be easily examined with the command:

       egrep -av '^[X#]' shar.file

It's hard to advocate for their use in good conscience, much like it's 
hard to advocate curl|sh pipes.

Review: https://reviews.freebsd.org/D48130

Thanks,

Kyle Evans