!includedef support

[jvmlet]

Please support !includedef syntax, below diagram renders empty output when mouse is on both @startuml lines :

@startdef(id=main)
actor Bob $color
Bob->Alice : hello
@enddef

@startuml
!$color = "#red"
!includedef  main
@enduml

@startuml
!$color = "#Blue"
!includedef  main
@enduml