Fix show less/more button occluding the list automatically
When the user would click 'show more' they would be presented with a 'show less' button that occluded the last room.
Similarly, if they resized the list so that all their rooms would be shown and refreshed the page, they would find their last room covered by the button.
This changes the handling so that showAllClick() sets the height to numTiles + button padding, and adjusts the height calculations on render to deal with relative tiles.
This also removes the conditional padding of the resize handle, as we always occupy the 4px of space. It was leading to rooms getting trimmed slightly by the show N button.