Refactor the Lab's core UI plugins for code separation [was #7830]
Some tool specific stuff isn't in the tool plugins, but somewhere in the core UI stuff. E.g., the tool menu items are in itl.core.application, some perspectives are defined in the welcome screen etc.
This causes unneeded dependencies (which may cause trouble themselves), and it makes it hard to temporarily disable a tool (because you can't just remove it from the product definition, but need to touch the core stuff, as well).
Basically, itl.ui.core shouldn't depend on any GUI plugins from the Lab, the application and welcome stuff shouldn't depend on tool-specific plugins etc.