This greatly simplifies the folder highlighting logic. It wasn't clear
before and the code was probably doing more than it should. The logic
with highlight_opened_file wasn't working at all, so i just removed it.
This should allow us to greatly extend the order in which the components
are rendered.
- use a builder pattern to mount the lines / highlights
- i think we lost a little performance, but gain in design
- code for file/folder icons is abstracted in components/icons.lua
- should also fix the issues where vim.g variables where loaded before
setup.
