libshell: Renamed TextEditWidget -> LineEditWidget

A more descriptive name for the class.
Documentation: Added Doxygen config for libshell API docs

Also included in the Builder for nightly updates.
libshell: Added Action and LabelWidget
libshell: TextCanvas interface improvements, handling Actions
qmake|Mac OS X: Tweaked deployment of shared libraries
Doom64|Fixed: Compiler warning about pointer types
libdeng2|Refactor: Revised RectangleRule and DelegateRule implementation

RectangleRule was improved so that the horizontal and vertical rules
are separate from each other: invalidating a horizontal input will
only invalidate horizontal outputs.
libdeng2: Improved Observers macros for more versatility

It is now possible to declare an observer interface outside a class.
libdeng2|Refactor: Replaced Qt signals with de::Observers in Rules and Clock

de::Observers has less overhead and does not require an additional
base class (QObject).