Improve styles of multiview demo

Incorporates layout styles from the version on dgrid.io
Move documentation from the GH wiki into the repository

Based on @edhager's work of similar nature for 0.4
Docs: Mention `dgrid-autoheight` (added in 0.3.14) in migration docs
Update version for tag
Update version for dev towards next 0.3 release
[FIX][MOVED-FROM-EXTENSION] scroll columnset when single row is rendered and scrolled
[FIX][MOVED-FROM-EXTENSION] support column hider on columnSet
[FIX][MOVED-FROM-EXTENSION] emit load page event + removed tab index + total handling (*)
[FIX][MOVED-FROM-EXTENSION] support for startup widgets, support for rowListeners
[FIX][MOVED-FROM-EXTENSION] support for nested properties & defaultRenderCell overriding
[FIX][MOVED-FROM-EXTENSION] support for canceling previous refresh, unknown total & grid-no-data class
[FIX][MOVED-FROM-EXTENSION] support overiding error handling, custom no-data-class, empty array as sort