Dynamically size Scribe command UI

[andrewtavis]

This issue is a major priority for Scribe's UI. What's needed is edits to KeyboardViewController.swift and Keyboard.xib files to make Scribe keyboard elements dynamically sized. As of now the height of the Scribe key, command bar, and other command keys is set by Keyboard.xib, whereas it should instead be sized within KeyboardViewController.swift so that the height can account for the keyboard height.

Of importance is that the aforementioned elements are currently taller than they need to be, which then reduces the available space for the keys. Keys on Scribe keyboards are currently slightly smaller than system keyboards and closer together regarding the y-axis, so it would be better to reduce the height of Scribe command elements so that it can be used to properly layout the keys.

This issue can also include a check of keyboardHeight in KeyboardViewController.swift, which could also be dynamically sized.

[andrewtavis]

A potential solution to this is linking the height of the command elements - the Scribe button, command bar, and other command buttons - to the stack views on which the keyboard buttons are laid out within Keyboard.xib.

[andrewtavis]

The above comment was implemented in d6c4ed9 for the design sprint in #112 to close this issue. The elements of the Scribe command interface are sized dynamically to a background element that's sized relative to the stack views.