When a snippet is submitted, but there's an error, we didn't keep the
visibility level. As the default is private, this means that submitting
a public snippet that failed would then fall back to being a private
snippet.

Add new global application settings for default project and snippet
visibility levels.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Project - restyled show page, removed info page
Repository - restyled show page, added download option
Tags - added download options