WIP, Rename entry to palette, remove root type

[rockitbaby]

(opening this pull request, to have a place for discussion with @halfbyte and @theflow)

my goal is to establish the following model of an oco file as good as possible in the core of the library, so all parts of oct are based on a common well formed understanding of oco.

• a palette can contain entries.
• entries are of one the following types: palette, color, reference
• every entry, independent of its type has a name.
• every entry but root belong to a palette, its called parent (either the file or another child palette, defined by an entry type)
• the name an the relation to the parent are used to form the path (dotpath)
• every oco file is a palette without a parent

do you agree on the model?

as a first step i renamed 'Entry' to 'Palette' to be more meaningful.
root is defined by the fact that entry.parent is null.

this change causes some refactoring in renderer and companion app (basically just search and replace type checks).

continue?

[halfbyte]

LGTM. Looks like a nice improvement to me and as long as it helps/helped you express stuff better, I'm all for it.

As I don't want to interfere with your development schedule, please merge this on your own whenever you're ready for it.

❤️ ❤️ ❤️