libdeng2|Animation: Added copy constructor and assignment operator
libdeng2|OperatorRule: Convenient way to construct a Maximum operator
Fixed|Client: Build failure
Client: Interaction between console and log widgets

When new log entries arrive, the console widget's height increases
accordingly. Added a content Y offset to the log widget to allow
syncing it with height increases.
Client|Widgets: Simple gradient frame for the button widget
Client: Cleanup
Client|LabelWidget: Image scale modifies source image's effective size
Client|TaskBarWidget: Basic elements

Added current game mode indicator and the engine version number with
a DE logo.
Client|ConsoleWidget: Improved integration with LogWidget

When in non-expanded mode, the console will expand the console when
pressing PageUp/Dn, instead of scrolling the log.