Provides ref concepts to yaml layouts

This MR provides ref concepts to widget layout.

• Allows to specify component ids such as foo.bar
• A specific property value can be used by hardware objects to ref another object
  • hardware:foo (refers to the hardware object foo)
  • hardware: (refers to nothing)
• Plus tests
  • Tested with mocked objectref pointing to omega/omega1 motors
  • Tested layout widget with initial state and updated refs
  • Tested with single foo.bar and double reference foo.bar.bar

Relative to daiquiri!344 (merged) and daiquiri#3