Breadcrumb control: add the flag 'noLink' to display breadcrumb fragments as static text

[lscorcia]

Hello,
this pull request adds the following enhancements:

• Fixes the import of Observable from rxjs (Issue app-breadcrumb.service.ts has wrong import from "rxjs" so causes overhead in resulted bundle #22)
• Allows a custom data flag called noLink on routes that makes it possible to display "disabled" fragments in the breadcrumb bar (Issue Breadcrumb - Allow breadcrumbs without link #29). Example below:

To use this, users would have to set the noLink property in their app.routing.ts file, e.g.:

...
{
    path: '',
    component: DefaultLayoutComponent,
    data: {
      title: 'Home'
    },
    children: [
      {
        path: 'base',
        data: { noLink: true },
        loadChildren: './views/base/base.module#BaseModule'
      },
      {
        path: 'buttons',
        loadChildren: './views/buttons/buttons.module#ButtonsModule'
      },
...

The modification itself is quite simple and probably noLink isn't the most intuitive of property names but feel free to change it if you find something better.

• Removes build artifacts from the repository (makes diffs easier)

Thanks for your consideration and for your great work.

[github-actions]

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