[components] refactor main template header: make it much more flexible by using CtxComponent * rename userlink class (not private) with somewhat bw compat * make some cosmetic adjustements on log-in/registration components * update to component api, though this may breaks some sub-classes (for application customizing the breadcrumbs component for instance)

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body { background-color: %(bgcolor)s

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       font-size: 100%;

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     }