Fixing the mesh hide selector in the editor.

[itsmeted]

There is a bug where selecting the triangles when editing a mesh hide asset does not get the correct rectangle for doing an area select of the triangles. This fix correctly transforms the coordinates of the selection rectangle to screen coordinates in order to perform the selection correctly.

[itsmeted]

@Jaimi Here's the pull request to develop. Please review

[Jaimi]

Thanks - I'm waiting to merge this until after my massive pull-request is merged.