Tooltip Widgets

Adds support for generic tooltips as widgets. These can be declared in ui files, or constructed at runtime. I believe this also allows for extension, by wrapping in a layout and decorating with further widgets.

Additionally, .ui files now support a simplified declaration of UILabels as simple strings - anywhere a widget can be declared a string can be used instead and that will be interpreted as a UILabel. Obviously allows for the tooltip declaration, but can also be used anywhere else a label may be desired. See the videoMenuScreen.ui for an example.