Introduce GPG operations

Add methods for cryptographic authentication of Cask packages with
the GPG software suite.

Homebrew Cask invokes the system-standard `gpg` binary to import
keys to the GPG keychain, download signatures to versioned metadata
folders, and verify packages. Homebrew Cask aborts if any step fails.

GPG verification is not currently invoked during the audit or
installation processes, and is intentionally left undocumented.

Example usage:
    gpg = Cask::GpgCheck.new(cask)
    gpg.verify(package_archive_path) if gpg.available
Update Clion to 140.569.17
Merge pull request #7677 from weijianwen/clion-140.569.17

Update Clion to 140.569.17
update pycharm to 4.0.1
upgrade pycharm-ce to v4.0.1
Merge pull request #7678 from elnappo/patch-1

upgrade pycharm to v4.0.1
updated arrsync ('0.4.1')
Merge pull request #7679 from vitorgalvao/update-arrsync

updated arrsync ('0.4.1')
Add Tuck
Merge pull request #7680 from qqshfox/tuck

Add Tuck
Update sogouinput.rb

Update.
Merge pull request #7682 from vitorgalvao/fix-7681

Update sogouinput.rb
revise accessibility methods in postflight miniDSL

* rename `remove_accessibility_access` to `disable_accessibility_access`
  to match corresponding method `enable_accessibility_access`
* move `TCC.db` and `.AccessibilityAPIEnabled` paths to `Cask::Locations`
* remove unneeded backslash from `TCC.db` path
* use full paths to `touch` and `sqlite3` utilities
* use `@command.run` instead of `system_command` which is intended as an
  external interface
* reverse conditional so enable/disable logic is consistent
* `sudo` is needed when creating `.AccessibilityAPIEnabled`
* instead of silent fail, warn that access cannot be safely disabled on
  Mountain Lion and earlier (it could, but might affect other apps)
* quoting/whitespace
revise plist methods in postflight mini-DSL

* accept index argument to `info_plist` in case of multiple `app`
  artifacts, defaulting to first
* return `Pathname` object from `info_plist`
* use `@command.run` instead of `system_command` which is intended
  as an external interface
* quoting
revise move_to_app method in postflight mini-DSL

* use `@command.run` instead of `system_command` which is intended
  as an external interface
* quoting
Add cask for Avast Mac Security

Create a cask for Avast Mac Security. Not entirely sure if the
uninstall stanza is correct. The dmg comes with an uninstaller
with the filename 'com.avast.uninstall.app', but I can't find
anything in the docs about using a pre-packaged uninstaller.

Remove broken uninstall stanza

Add uninstall stanza suggested by @rolandwalker

This stanza seems to work. Application and support files all removed
after uninstall.
Add FingerLock.app version 1.0

FingerKey makes it easy to unlock your computer without having to type your password every time.
Update WD Security to 2.0.0.30
Merge pull request #7675 from jawshooah/add-avast-cask

Add cask for Avast Mac Security
Merge pull request #7687 from vinkla/fingerlock

Add FingerLock.app version 1.0