build: udpate solution file to fix the bug:

http://kasperholdum.dk/2014/01/a-numeric-comparison-was-attempted-on-targetplatformversion-evaluated-to-empty-string/
build: create a new project - Experiment.Idioms.
build: create a new test project - Experiment.IdiomsUnitTest.
build: install xunit package to Experiment.IdiomsUnitTest.
build: install Albedo package.
build: install xunit package to Experiment.Idioms.
dev: introduce the IdiomaticTestCommand class.
dev: add guard clauses.
dev: implement the Timeout property.
dev: implement the DisplayName property.
dev: implement some properties.
dev: implement ShouldCreateInstance property.
dev: implement the Execute method.
dev: introduce IdiomaticTestCase.
docs: improve XML document on the constructor of IdiomaticTestCommand.
dev: add guard clauses to IdiomaticTestCase.
dev: implement some properties of IdiomaticTestCase.
dev: implement ConvertToTestCommand method.
build: address some code-analysis warnings.
dev: introduce IdiomaticTestCaseCollection.