Hbc is the namespace, Hbc::Cask is the object representing a Cask
One step on the path to reducing the surface area of the God-object
we've grown over the years. :)
Let the terminal decide how to display bold. Fixes#9349.
The issue arose when integrating Homebrew's `Tty` class.
Homebrew's `Tty.white` actually emits escapes for bold.
Fixing `Tty.white` to do what the method name says caused
loss of visibility on light backgrounds.
* convert existing Cask:: namespace to Hbc::
* move Homebrew-fork code under Hbc::
* move freestanding classes such as Tty and TopologicalHash under Hbc::
* recast HOMEBREW_CASK_ constants as HBC_
* modify our Homebrew Formula for backward compatibility
* devscripts and dev docs
