libdeng2: Fixed build and removed redundant functionality in LogSinks
libdeng2: Added copy constructor for LogEntry::Arg
libdeng2: Adding and removing sinks to/from a log buffer
libdeng2: Added a way to adjust line width of MonospaceLogSinkFormatter
libdeng2|Refactor: Improved API of TextCanvas

Drawing a canvas onto another canvas.
Shell: Basic LogWidget functionality

The log widget has a sink for log entries, which are then rendered
onto the screen.