Fix for issue with nested givens having their setup actions called multiple times

A fix for this issue described in a previous pull request:

For example, consider a test laid out like this:

When(something)
Given(given 1 action).Verify
Given(given 2 action).Verify
Given(given 3 action).Verify
Then(verify some expected state)

Given 1 action
Given 1 action (again) -> Given 2 action
Given 1 action (againt) -> Given 2 action (again) -> Given 3 action -> When -> Then

The commits in this request have two possible ways to fix this:

1 - Add a flag to the 'context' class to figure out if the context setup action has already been invoked.
2 - Remove what appears to be an extraneous call to 'InitializeContext' from within the VerifyContexts method