Legacy features migration (following needs)

[magicoli]

Eventually, all features currently provided by legacy code must be adapted
to use the new environment. This could be made progressively, following the
needs of tasks being processed. No fundamental change must be done inside
legacy/ folder. If a feature is modified, fixed or enhanced, it has to be
moved to the new environment at the same time.

Tasks

• directory structure scan
• page rendering
• client video uploads (currently external library)
• global, per client and per project preferences (currently config files)
• pages and sidebar contents (currently pseudo markdown text files)
• playlist editing (currently manual, text file)
• tags and categories (currently pseudo sub directories)
• video editing (currentaly manuel, text files and CLI scripts)
• zip file generation for downloads (currently manual)