Allow tasks to be scored manually

There are some tasks, like essays or retrospectives, that we want the
admins to score instead of having an automated test.
Improve spec naming

Those refer only to automatically scored tasks, not all tasks in general
Allow solutions.points to be null

This lets us distinguish between scored solutions and unscored ones.
Move to next unchecked solution

This makes it easier for admins to manually score tasks.
Oops. Typo
Merge branch 'manual-scoring'
Refactor a stepdef
Remove 1.9 encoding tags