Lab bugfixes: Layout & deletion of selected service

Fixed:
- A service deleted using the right-click menu is still selected and causes the add plugin window to break when adding a plugin.
- Graph des not display any vertices when only one exists using most layout. (NB: This is a GraphX bug. As a workaround, I'm now using a default layout that works.)
Lab bugfix: Services and plugins could be removed while engine is running.
Lab: Show a basic MessageBox when Engine startup fails.