BUGFIX: don't try autocleanup inside system dirs

This safety feature addresses #2650 somewhat indirectly.
A list of system directories is defined.  When the uninstall
process encounters a "system directory" it does not touch that
directory at all
- no chmod on that dir
- no search for broken symlinks in that dir
- no cleanup of .DS_Store files in that dir
Explictly listed files from a pkg receipts are not affected by
this change.  Individual files will still be removed, even if
those files are in a special "system directory"
Emoji and disk usage stats at install success

- consistent with Homebrew output
- respects Homebrew environment variables
- does not add any Homebrew code dependency
- really just for fun
accept multiple arguments to uninstall/:pkgutil

We may as well do so, the previous behavior was a bug:
multiple elements were silently concatenated into a single
regexp.
demote FAQ.md to doc directory

This doc currently has very little content.  Also fix link
text for other content in the doc directory.
update adobe-air Cask to use list form of system

and full path to sudo, with -E and dashdash
wireshark after_install: full paths/formatting

full paths to utilities is preferred
mamp.rb after_install: use full paths to utils
github.rb after_install: use full paths to utils
alfred.rb `after_install`: full paths+list form

use safer list form of `system`.  use full paths to external
utilities.
bartender.rb `after_install`: full paths+list form

use safer list form of `system`.  use full paths to external
utilities.
daisydisk.rb `after_install`: full paths+list form

use safer list form of `system`.  use full paths to external
utilities.
f-lux.rb `after_install`: full paths+list form

use safer list form of `system`.  use full paths to external
utilities.
houdahspot `after_install`: full paths+list form

use safer list form of `system`.  use full paths to external
utilities.
fantastical `after_install`: full paths+list form

use safer list form of `system`.  use full paths to external
utilities.
kaleidoscope `after_install`: full paths+list form

use safer list form of `system`.  use full paths to external
utilities.
path-finder `after_install`: full paths+list form

use safer list form of `system`.  use full paths to external
utilities.
alib1.rb `after_install`: list form of `system`

use safer list form of `system` and simplify quoting
chunkulus `after_install`: list form of `system`

use safer list form of `system` and simplify quoting
heart.rb `after_install`: list form of `system`

use safer list form of `system` and simplify quoting
remove constant HOMEBREW_TAP_FORMULA_REGEX

we no longer need to set this, as Homebrew added it to
testing_env.rb