Modularity (WIP - Do not merge)

This PR introduces mixins in a really simple format. Creates some functional mixins and applies those to refine and refactor view, with full backwards compatibility.

Opening this PR for discussion.

/cc @sinan @szkl @gokmen @fatihacet @canthefason @burakcan 
Should `parent` be notified about this by an event? `KDView::orphanize` manipulates subview list of a view but I think it should be responsibility of the `parent` view. Event handler method could be overridden in child classes as well.