Remove dependency of NUnit from AllureCSharpCommon.

[arpitgold]

AllureCSharpeCommon is common library for integrate Allure with C#. But it has a dependency with NUnit. So user (like me) who is not using NUnit in there project, bound to use NUnit.
This pull request removed dependency of NUnit from Core framework(AllureCSharpeCommon). So that user can use it with any testing Framework like : MSTest, XUnit etc.

[vania-pooh]

@arpitgold the build should pass to merge this.

[arpitgold]

Hi vania-pooh,
I am not sure, Whether it is a correct implementation or not.
I know its not a right way to change a testcase. So I am closing this pull request. Please check whether It can be possible to remove NUnit from AllureCSharpCommon by your own implementation.

Thanks
Arpit

[arpitgold]

Hi Ivan,
Can you please look into it.

Thanks
Arpit

[ilya-murzinov]

@arpitgold
Well, ok, I understand the problem, but you solution doesn't seem right, because you added your own exception and it will never be thrown.

The problem is that in Java there is java.lang.AssertionError which is supercalss for any exception which test frameworks throw. So any exception in Java is java.lang.AssertionError.
But in .NET there is no base class for exceptions so it's impossible to distinguish them crom other exceptions without dependency on concrete test framework.

This problem needs further investigation.

[arpitgold]

Yeah, that's correct. Please look into it, if you found any solutions for this.

[arpitgold]

Have you got the time to look into it ?

[vania-pooh]

@ilya-murzinov thoughts?

[ilya-murzinov]

see #9