core: i18n welcome page with branding

- Updated welcome page to take branding into account.
- Added ability to add multiple sections with links.
- Updated styles to take branding into account.
- Created new resource bundle for welcome page based on
branding manager.
- Added new application type to BrandingTheme, 'welcome'
- Added ability to put header text at top of welcome page.

Change-Id: I9987ed58c2e0ead9b25c5f46fb974a96bfd46d30
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=838456
Signed-off-by: Alexander Wels <awels@redhat.com>