ApplicationShellOptions are not used on ApplicationShell

[martin-fleck-at]

Bug Description:

When binding custom ApplicationShellOptions, they are not properly applied in the ApplicationShell due to a missing assignment.

Steps to Reproduce:

1. Use a custom re-binding in your application, e.g., rebind(ApplicationShellOptions).toConstantValue(<ApplicationShell.Options>{ leftPanel: { initialSizeRatio: 0.5 } }); or replace the binding in Theia with something that has values (https://github.com/eclipse-theia/theia/blob/master/packages/core/src/browser/frontend-application-module.ts#L163)
2. Ensure your workspace layout is reset to default.
3. Expand the left sidebar and see that the wrong ratio is used.

Additional Information

• Operating System: any
• Theia Version: master