HOLD for next release: Excalibur cask

Adding a cask for Excalibur; HOLD for next release since this required an
exception for Sourceforge URL's.
Use `stage_only` in atom-shell
Use `stage_only` in node-webkit
change version to 3.5.0, adjust url
Upgrade Adobe Lightroom to 5.7
Upgraded Opera to 25.0.1614.71
fix old-style header line in test suite
require new-style header lines

and enforce that the cask name (per the header) must match
the filename
Merge pull request #7448 from drvdijk/adobe-photoshop-lightroom

Upgrade Adobe Lightroom to 5.7
Merge pull request #7449 from crainiarc/opera

Upgraded Opera to 25.0.1614.71
DSL: remove support for `nested_container`

Obsoleted by new form `container :nested`.

This PR only removes DSL support; the job is incomplete.
Internally, `container :nested` is still implemented as a
pseudo-artifact named `nested_container`.  The intention
is to factor nested containers out of artifacts.
Update rubiTrack.app to 3.4.7
avoid gitx in partial-match search tests

Some gitx Casks are being renamed.  Refs: #7436
Added Deezer (Beta) v0.9.9_4104
Update wacom-tablet to version 6.3.10w2
Merge pull request #7455 from ohammersmith/wacom-tablet

Update wacom-tablet to version 6.3.10w2
Merge pull request #7452 from jconley/rubitrack

Update rubiTrack.app to 3.4.7
Merge pull request #7447 from MoritzFago/master

change version of Xmind to 3.5.0, adjust url
Merge pull request #7454 from fharbe/deezer

Added Deezer (Beta) v0.9.9_4104
Upgrade Biicode to v1.11