review of PiTiVi 0.13.x's render dialogs and project properties

The problems:

• redundant stuff creates confusion
• settings not remembered
• commonly used settings painful to reach for (especially due to the previous point)
• less commonly used settings thrown in random order alongside the more crucial settings (like bitrate and amount of passes)
• huge dialogs vs very small ones

Solutions:

• kill the settings in the project properties such as codec settings; only keep stuff that affects how the previewer behave (such as resolution)
• present more crucial settings in the main render dialog
  • kill the static labels, replace them by actual settings widgets
• save all settings used in rendering in the project; depends on bug #579531
• provide a "reset" button in the "advanced [codec] settings" dialogs

General design principles:

• the user won't care about setting the number of threads/cores manually; he wants to automatically squeeze as much juice as possible out of his multi-core processor without needing to think about it
• number of passes (and maybe some other quality settings like "decomb") should be controlled by one single checkbox: "draft mode" (no special effects, single pass, no deinterlacing, etc.)
• presets are not really that important, in my humble opinion; just making sure the container+codecs combo is actually valid, which we already do
• resolution, aspect ratio, should be derived from the project settings; the user would simply have to "scale" the image to the desired export size
• the project settings should allow entering metadata (title, author, copyright info, date, thumbnail, etc) that will be used in the render