sanity check against deleting user files

Needed to reduce danger from typos in "zap" stanzas.

As noted in the comments, this is somewhat simplistic, and
should later be merged with similar logic in lib/cask/pkg.rb.
Delete malfunctioning Codeplex casks, fixes #6618

pcsxr, wabbitemu and winxound casks were using a URL that lasts only for
24 hours. These casks never worked. There is no way to get a permanent
URL from Codeplex, and that means there is no way to fix those casks.
Add Progressive Downloader v1.7.2 cask

See <http://www.macpsd.net> for more info.
Add Not Pacman v1004 cask

See <http://stabyourself.net/notpacman/> for more info.
Add Not Tetris 2 cask
Add Order of Twilight cask
Add Ortho Robot cask

See <http://stabyourself.net/orthorobot/>. This game is open-source:
http://stabyourself.net/dl.php?file=orthorobot/orthorobot-source.zip
Specify that VMWare Fusion is commercial software
Specify that Moom is commercial software
Specify that Parallels is commercial software
Merge pull request #6630 from yegortimoschenko/avoid-codeplex

Delete malfunctioning Codeplex casks, fixes #6618
Specify that OmniFocus is commercial software
Specify that Kaleidoscope is commercial software
Specify that Skype is free closed software
Specify that Adobe Creative Cloud is commercial software
Specify that Notational Velocity is under GNU GPL
Specify that Spotify is gratis
Specify that Transmission is under GNU GPL

https://trac.transmissionbt.com/browser/trunk/COPYING
Specify that Seil is in the public domain

https://github.com/tekezo/Seil/blob/master/COPYING
Specify that Hex Fiend is under 2-clause BSD

http://ridiculousfish.com/hexfiend/files/License.txt