[IDE] Refactor the perspective shell to be a SPA

[StanZGenchev]

Is your feature request related to a problem? Please describe. In Dirigible, each page is called a "Perspective" and it contains two main things:

1. Shell This contains the header, sidebar, statusbar, perspective container and some common APIs.
2. Perspective This contains the layout, all views and Perspective API.

When a user selects a perspective from the sidebar, the entire shell (and therefore page) is reloaded. This is not only bad UX but it also creates some problems when we try to embed one perspective in another or try to have multiple perspectives running side-byside.

Describe the solution you'd like The Shell should be a Single Page Application that contains multiple perspectives and is able to switch between them without reloading. Perspectives should be embedable as well.