SwfTexture rendering improvements

Features:

1) Renders display object to target size directly from vector renderer (as per Issue #32), unless display object contains children with filters.  

2) When display object contains children with filters, calculates full visual bounds and scales to target size from bitmapdata of scale 1 vector render.  
    -  Fixes cropping of filter pixels in textures
    -  Allows filter settings within a display object to "scale" with exporter scale settings.

These features are beneficial independent of the bake-in-filters feature (separate pull request).