Hide component/version when not in use

When no components are defined for the project, the field should not be shown on the create screen, even though it is part of the screen and field configuration. It is the same for the version field. As it is now the fields are shown as Component: None, when no options are defined.

The reason is a have multi projects using the same screens and field configurations, but only som of them use components and/or versions. So instead of having to create field configurations and/or screens for all the projects, this is much smarter. Additionally, this makes it possible for the project admins to decide whether or not they wish to use the fields, instead of a global admin.

In addition, this is actually the way security levels work. Even though it is represented on the screen and shown on the field configuration, it is only visible for project where an issue security scheme has been set up. This behaviour is really nice, as only some projects need security levels.