Reorganize the chapters into parts and reduce the TOC depth to make the
TOC useful again. The top-level TOC is very brief, but that is fine
because every part will have its own TOC.
Section titles of languages/frameworks are also simplified to just
the name of the language/framework.
The `name` arg of `vim_configurable.customize` does not only determine
the package name, but also the name of the command/ executable to be
called.
In my opinion this is not documented properly and finding that out took
me several hours.
A new python script has been added to replace the aged viml-based
updater. The new updater has the following advantages:
- use rss feeds to check for updates quicker
- parallel downloads & better caching
- uses proper override mechanism instead of text substitution
- update generated files in-place instead of having to insert updated plugins manually
Automatically reading `dependencies` from the plugins directory has been
not re-implemented.
This has been mostly been used by Mark Weber's plugins, which seem to
no longer receive regular updates.
This could be implemented in future as required.
