Instead of having definitions of the
SfxCharmapContainer methods interspersed with those
of the SfxCharmapCtrl one in the same source file, move
them to an own source file.
Also move the class definition to an own header for
consistency.
This makes it a bit easier to keep an overview.
Change-Id: Ibf05b564e5936bee2bfda612b43fe0ecac26ddc6
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/195345
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>