Samples have missing parenthesis in LAYOUT_* macros

[BenEAVE]

It seems that the preprocessor has deprecated zero-argument macros without parenthesis in a recent version of PlantUML. So all of the samples that use LAYOUT_WITH_LEGEND or LAYOUT_LEFT_RIGHT fail to compile with a syntax error

@startuml Gives a lovely picture
!includeurl <C4/C4_Context.puml>

LAYOUT_WITH_LEGEND()

Person(admin, "Administrator")
@enduml

looks like this

@startuml Gives a syntax error
!includeurl <C4/C4_Context.puml>

LAYOUT_WITH_LEGEND

Person(admin, "Administrator")
@enduml

gives syntax error

I don't really fancy being the person to fix up all of the samples myself, but someone has to... I think this may also be the explanation for the issue described in #78

[BenEAVE]

I see that this issue is a duplicate of #23

Closing