Add on_initial_step_end().
Work on Adaptivity.
Progress on unification of adaptivity mechanisms with the rest of the code.
More adaptivity-related progress.
Add 01-intro.
Progress on adaptivity.
Progress on Adapt.
Fixes in test examples.
Finish with the adaptivity reorganization for now.
Redo test examples.
Revert Newton according to devel.
Progress on Adaptivity.
Fixes.
Progress on clearing up adaptivity.
Fixes in PicardSolver.
Code cleaning.
Delete unsuccessful historical attempt to implement local projections.
Reorganization.
Code cleaning.
More code cleaning.