Delete all selected items

REVIEW: 102337

Currently, if you select multiple items and press Key_Delete, it will
delete the current item (the last one selected). This patch makes it
delete all items.

To do that :

- We are started from the Aaron's patch
- We split the item list selected by type ( ProjectTodo, StandardTodo, Category
).
- For type ProjectTodo and Category, we remove the item from the list if the parent is
also in the list.
- For type StandardTodo, we remove item from the list if an ancestor
project is in project list.
- We add removeProjects in TodoHelpers.
- We add removeCategories in CategoryManager.
- We pass the list to the TodoHelpers for projects and todos list and to
the CategoryManager for categories list.