First draft for the support of nullables (with one test related to the IsZero() assertion).
Adds few assertion methods for nullable types that cover numbers (e.g. int, double, long, etc): IsNull(),  IsInstanceOf<T>.

Generates code and tests for all number types.
Adds unit test dedicated to the IsInstanceHelper class.
Adds regions within the <number>RelatedTests files.
Adds the IsNotNull() assertion method for nullable numbers + related tests.
Adds a comment indicating that we could enable the IsNotNull assertion on nullable to return a chainable assertion ONLY if we introduce the capability to disable/hide the Not operator for some methods.
Updates the release note.
Adds the assertion method IsEqualTo() to nullables of numbers.
Dismantles the IsNull() and IsNotNull() assertion methods for nullable numbers, and replaces them by the HasValue() and HasNoValue() methods instead.
Finishes the support of the assertions on the nullable numbers by adding the capability to chain the HasAValue() assertion with a new Which operator that allows us to assert on the number of the nullable.
Adds a code sample for the nullable assertion within the readme.md file.
Re-generates all the number related tests.