Getter and setter methods for title, author, datadir and theme

Getter and setter methods for title, author, datadir and theme for correct access to the slots of the object

With this solution, our users now have to remember that

1. Interactivity can be fetched/set with interactivity() and interactivity() <-
2. all other functions work with a get_ and set_ prefix.

Why not add getter/setter methods 100% analogous to the interactivity-function? This would allow:

# Get title
title(dashboard)
# Set title
title(dashboard) <- "New title"

and it would be much easier to remember...

added 1 commit

• 22fad866 - changed naming of getter and setter methods

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merged

mentioned in commit 6c1ffd72