fix bug, when declare is a virtual one, the update view frame and fillview will return in correct frame.
when fill into an external view, the library will create a wrapper declare for it. This enables the use case that directly specify magic value in the root declare.
use ivar instead of property internal.
No more sync frame back & forth, now when eternal client set frame, the frame go directly into unexpandedFrame, and set the layout to non expanded, and keep the old frame value not changed. Then the user call fill view or update frame, the frame will be recalculated.
Merge branch 'master' of https://github.com/shuoli84/FlexibleView2