Add canvas rotation function.
Merge branch 'dev' into rotation
Merge branch 'rotation' into 0.51

Conflicts:
	src/painttyDesktop/widgets/canvascontainer.cpp
	src/painttyDesktop/widgets/canvascontainer.h
增加画布旋转的界面控制。

Signed-off-by: liuyanghejerry <liuyanghejerry@126.com>
完成画布旋转功能。
closes #33

Signed-off-by: liuyanghejerry <liuyanghejerry@126.com>