recast method `destination_path` as `staged_path`

* part of DSL 1.0 review
* `destination_path` was always a bit vague (it refers to
  Cask-specific, version-specific location under
  `/opt/homebrew-cask/Caskroom`)
* here renamed `staged_path` to match upcoming command verb
  `brew cask stage`
* rename also intended to reduce confusion when we implement
  copying as a configurable alternative to symlinking
* transitional `destination_path` methods to remain while
  Casks are converted (this was documented as a part of the
  DSL, and used by 39 Casks in main repo)
* unrelated variables containing "stage" recast for clarity
reuse version in boom-recorder.rb
reuse version in fliquo.rb
reuse version in geneious.rb
reuse version in jabber-video.rb
reuse version in preform.rb
reuse version in sauerbraten.rb
reuse version in slender.rb
Upgrade Fritzing.app to 0.9.0b
added yummy ftp
Merge pull request #6824 from albertico/fritzing

Upgrade Fritzing.app to 0.9.0b
Merge pull request #6808 from pan-long/add-yummyFTP

added yummyftp
Upgrade DeathToDSStore.app to v1.0.4
Upgrade MacPorts to v2.3.2 and add Yosemite support
Merge pull request #6828 from fenhl/patch-1

Upgrade DeathToDSStore.app to v1.0.4
Merge pull request #6829 from diimdeep/macports

Upgrade MacPorts to v2.3.2 and add Yosemite support
Merge pull request #6785 from rolandwalker/reuse_versions

Reuse version number in 7 Caks
Merge pull request #6783 from rolandwalker/rename_destination_path

recast method `destination_path` as `staged_path`
Add MagicPrefs Latest

Added MagicPrefs Cask, it uses the latest version available
Merge pull request #6826 from andres-torres-marroquin/magicprefs

Add MagicPrefs Latest