Convert blocks to widget

[vanyle]

Block should be widgets instead of QGraphicsItem.

This would enable several things:

• Because widget can be embedded inside other widget, we could add a QGripSize to not reimplement the resizing of blocks.
• We could also add a QSplitter widget to separate the output panel and the code editor for better sizeing.

This would reduce the amount of ui code we have to implement are reduce ui bugs.