Fix failing crontab job.  Simplify email secrets handling.

After adding ~/Dropbox/proj/dotfiles/bin to the path, the
new_oist_careers invocation in my .crontab was failing, because it was
hardcoded to ~/bin dir.

Removed the dummy .forward from dotfiles and replaced it with a real
.forward in my secrets.

Modified dotf to not replace dummy email (foo@example.com) with my real
email in .crontab or .forward.

Moved .crontab from copy/ to link_home/, so I can modify ~/.crontab when
I need to, instead of (laboriously) modifying
~/Dropbox/proj/dotfiles/copy/.crontab and redeploying it to ~/.  This
avoids the error of modifying ~/.crontab too.
Removed tasks deprecated by link task.

Moved .vimrc to link_home dir.
Renamed link_home to link.  Sounds cleaner.
Removed vimrc and bashrc tasks, since link task does what they do and
there is no reason not to just run link and do it all, since link files
do not need any secrets injected into them.