77 Improve startup time

Close #77.

This pull request started off by moving almost all logic from `plugin` to `autoload`. This lead to a big refactoring in the `autoload` part. I also started to extract the first parts into own subdirectories within autoload. I might start to extract the different logic for different text objects into similar parts.

Anyway, the startup time improved for me locally from `43.5ms` to `7.4ms`, shaving off more than 80%.

This also uses `<silent>` mappings as suggested in #88.