Replace InsetButton and ButtonInset with a ButtonRenderer that can be

Replace InsetButton and ButtonInset with a ButtonRenderer that can be
included as a member variable.
Enable InsetExternal to choose its renderer dynamically.
diffstat tells me
25 files changed, 627 insertions(+), 646 deletions(-)

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@7160 a592a061-630c-0410-9148-cb99ea01b6c8