docs: update dockLayout references

[miralemd]

BREAKING CHANGE: rect is now a reserved keyword for components

Breaking

A lot of examples used the beforeRender lifecycle method to set this.rect on the component:

beforeRender(opts) {	
  this.rect = opts.size;	
},

💥 rect is now a reserved keyword and automatically set on all components by the layout strategy. Trying to assign a value to rect inside a component will throw an error.

The actual breaking PR is #354, but it did not contain any BREAKING CHANGE comment, so adding it in this commit instead.

Deprecated

Properties related to the layout strategy have been moved one step down into a layout object, while dockLayout has been renamed to strategy:

Before

picasso.chart({
  settings: {
    dockLayout: { // deprecated, use strategy instead
      logicalSize: { width: 400, height: 300 }
    },
    components: [{
      type: 'point',
      dock: 'left', // deprecated, use layout.dock instead 
      prioOrder: 1, // deprecated, use layout.prioOrder instead
      displayOrder: 2, // deprecated, use layout.displayOrder instead
      minimumLayoutMode: 'SMALL' // deprecated, use layout.minimumLayoutMode instead
    }]
  }
});

After

picasso.chart({
  settings: {
    strategy: {
      logicalSize: { width: 400, height: 300 }
    },
    components: [{
      type: 'point',
      layout: {
        dock: 'left',
        prioOrder: 1,
        displayOrder: 2,
        minimumLayoutMode: 'SMALL'
      }
    }]
  }
});

[nilzona]

Maybe mention the change of dockLayout -> strategy property that is part of this PR?