Fix bug that previous select indicator display when star multiple select status.

Change-Id: I6b3d6641b9c26fd09f6fc6a74eae6ac28853ee8a
Little refactors.

1) refactor method to removeSelectedBorderDecorator(), no redarw or invalidate in it.
it  become more pure.
2) add UNKOWN_MODE to DrawingToolsManager, and PaintBoardView initialed with UNKOWN_MODE.
3) PaintBoardView register it self to DrawingToolsManager in it's contruct after all it's
field be initialed.

Change-Id: I65299832cc524ad61b7394d406029ef6e5113461