Introduce shooting

[rexim]

To Do:

• [x] Get rid of BulletSpaceModel
• [x] Clean up the code style
• [x] Unit Tests

@ForNeVeR even though this PR is WIP I'd like to ask you to review it anyway and provide as many comments and suggestions as possible. Since this is my first experience with C# I probably made lots of mistakes. Thanks!

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Close #5

[ForNeVeR]

There're some minor issues regarding the established code style (some of them are common practices and some of them're common rules I choose for this project):

• don't put space before function invocation parentheses: e.g. new BulletModel (this) should be new BulletModel(this)
• always put { onto the new line, except trivial properties like int Foo { get; set; } and one-line object expressions like new Barmaley { Foo = bar }
• use spaces and not tabs for indentation
• put a space between class name and : in declarations: class BulletModel : IModel

None of the issues are critical and there's no urgent need to fix them; please consider them when writing new code.

[rexim]

@ForNeVeR I think we are ready for the final review! I covered with UTs only what I saw makes sense to cover. Let me know if more is needed.

[Newlifer]

I second this!

[ForNeVeR]

Thank you! Rebased on develop.