Changes to default-style.lua:
Prevent text from being drawn past bounding box via love.graphics.setScissor().
The cursor and surrounding text are kept in visible range by calculating a draw offset.
Made a marginally simpler & more readable Slider draw routine using rectangles instead of lines.
Also the ends of the slider "track" are capped now. I split this commit in case a rollback is desired.
Slider, when vertical, was drawing the grab box with inverted position. Center "track" had incorrect orientation.
Also, slider.lua was passing a bunk table to group.getRect().
