create a default theme when SdrPage and SdrModel are created

For a document it is expected that it always has a theme available
so we need to create a theme with some default attributes set (a
default color scheme for now) when we create a SdrModel and SdrPage
(only for Writer currently).

This also changes some ColorSets, SdrPage, SdrModel methods, to use
better return types (cost& instead of raw pointers and vice versa
depending on the use case).

Change-Id: I874247784b845109e42567e3f45647dda46ccf3b
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/146816
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>

0 files changed, 0 insertions, 0 deletions