Implement elementary building blocks of userinfo

[smidl]

Userinfo classes should be lego-like, i.e. they can be composed into bigger blocks.

Key operations are:

• askuser() for interactive communication with the user, and
• build() which will create an object which is represented by the info.

[smidl]

Basic stuff is in place:

Files with most used classes have now *_ui.h counter parts.

Still, methods askuser are NOT implemented, This should be done as a separate task.