Replace some old pure python import by LodelContext calls
Change the plugins imports methods to use LodelContext instead
Fixes dyncode exposure method

- updated scripts etc
- make tests pass

Theorically all of those imports were tested by unit testing, but we've got no inssurance about that.
And even if unit tests had check for syntax errors, all pieces of code were not tested. We cannot
be sure that an import was missed or forgotten...