Over the past few years, the stellar British-born actress Sally Hawkins has been working steadily, but it’s been quite a while since she’s gotten a role that allowed her to steer a whole movie the way her critical-breakthrough lead in Mike Leigh’s 2008 “Happy Go Lucky” did. With “Maudie,” she has that and more.The film begins with a shot of Hawkins, looking old and frail, twisting her body as she dips a brush into a paintbox, and then, with seemingly great difficulty, applying some color to a simple flower design on the wall behind her. The shot brings up a number of questions: what is the character suffering from? Why is she painting flowers on the wall? And so on.