To enable rudimentary theming, collect all colors in a new
theme class. The class has to be passed down to the various
items.
In general the items save a reference to the them in the
constructor. Alternatively, they might also just query
the StatsView everytime they need to access a color.
For now, it's hard the say what is preferred: a reference
per item or a function call per invokation?
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
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