Modify Runner.Program.cs to support year selection.

[RedRabel99]

Add option to select a year by providing it as the first argument.

Possible arguments and what they do:

• No arguments - Solve last problem.
• all - Solve all problems.
• <year> - Solve last problem of given year.
• <year> all - Solve all problems of given year.
• <year> <problem1> ... <problemN> - Solve given problems of given year.

Replace assemblies list with dictionary and GetAssemblies method to get all assemblies or only the ones of the type of the given year.

The reason I suggest this change is because I wanted to solve a specific problem, but the runner ended up solving all problems of the given index across all years in the repository.

[eduherminio]

The idea looks good to me, and therefore might worth including it in this example/template.
I'm quite busy right now, but I'll have a proper look in a few days.