Add static code analyzer

[isalzh]

Description:

Need to be done:

• explore capabilities of the open source package named "StyleCop";
• attach StyleCop analyzer to every project in the solution (except Test projects);
• make "Solution Items" folder in the root of Teams solution;
• create a ruleset file with name "quiz.ruleset" with default set of rules and put it under the "Solution Items" folder.

Out of scope:

• do not make any code quality fixes.

Acceptance Criteria:

StyleCop should report all code quality issues as warnings to the Error List window of the Visual Studio.