[pkg] remove unused templates & scripts

branding/scripts/init

branding/templates/osx/cross-quickpkg

branding/templates/osx/generate.py

branding/templates/osx/quickpkg

branding/templates/osx/template-helper.plist

branding/templates/osx/template-info.plist

branding/templates/osx/template-packageinfo.plist

branding/templates/osx/template-postinstall

branding/templates/osx/template-preinstall

branding/templates/windows/generate.py

branding/templates/windows/payload/install

branding/templates/windows/payload/uninstall

branding/templates/windows/readme.txt

branding/templates/windows/template.nsi