improve project with doc and control
Project: add items method to return all items for a category
Add meta information for project categories
Use dynamic approach to display project summary
Save project after metadata changes
Rename project properties "category_keys" and "metadata_keys"
Merge pull request #81 from gbaty/dynamic_project_preview

Dynamic project preview
Merge pull request #78 from jucoste/improve_tuto_koch

Improve project tutorial_models (Koch)