UI: support simple layout alignment logic for 2D layer

[kikonen]

Orthographics "ui" layer needs some logic to allow aligning things against specific placement on viewport.

Ex. "align bottom, right", which should align mesh pivot agains given point. In viewporrt "bottom right" is not truly defined by [1, -1], since aspect ratio varies, thus when viewport changes will need to adjust somehow position (and size) of mesh, but retain aspect ratio.

Simple trick doing this is to enforce orthographic viewport to be in non-aspect-ratio scale, but this pushes problem in meshes, since then it' possible to use pivot [1, -1], but aspect ratio of mesh is invalid.

=> perhaps aspect ratio correction could be automatically applied in the scale of mesh?!? I.e. this could be a bit easier to manage (not sure) than adjusting position (and possibly more easy to understand layout when debugging or such).