Judge - Composite Strategies

[sheytanov]

The idea behind the composite strategy is the following:
Lecturers create different problems with different execution strategies in a contest:

When users compete in a contest they will have only one submission form. The problems will run sequentially and give different points. This way we can avoid situations where the users submit different code for a single problem. Basically one possible solution will be to create a facade over the existing contest menu and display a single form.