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).
libdeng2: Cleanup
libshell: Added MenuWidget
libdeng2|Refactor: RectangleRule is no longer derived from Rule

RectangleRule is not really a Rule instance, it only manages a complex
set of connections between input and output rules.
libdeng2|Shell: Improvements in the widget framework
libdeng2|Shell|Refactor: Renamed RectangleRule to RuleRectangle

RuleRectangle is a better name because the class is no longer derived
from Rule, and conceptually defines a rectangle made up from rules.
Shell: Added menu items, fixed MenuWidget
libshell: Added a utility routine for determining line wrapping
Shell: Adjusting menu items
libshell: MenuWidget's border style is configurable
libdeng2: Added Rectangle<>::adjusted()

Expanding or shrinking the size of a rectangle.
libdeng2|Refactor|Fixed: Improved Rules implementation

Rules are now passed as argument by const references rather than
const pointers. This allows overriding arithmetic operators to easily
create OperatorRule instances.

The OperatorRule operators return a reference to a refless rule
instance that the caller is expected to take a reference to.

Added a Floor operator to OperatorRule.

Rules are also by default invalid after instantiation.

DelegateRules inform their source when they become invalid so that any
internal dependencies can be resolved. Fixes a problem with
RuleRectangles where invalidating a Width or Height would not cause
the Left/Right, Top/Bottom edges to also become invalid.