'Promoted' BasicCookieStore to private class variable.

This is in preparation for adding a method to update the mimicked
Selenium cookies that will need access to the BasicCookieStore.
Added a new FileDownloader method, modifyMimickedCookieDomain.

This allows the caller to find a particular cookie that is being
mimicked and update the cookie to use a different domain. This
method was added to workaround an apparent InternetExporerDriver
defect. In my testing, the IE WebDriver ignored the domain for
cookies, and passed them as null to the FileDownloader; this
caused tests to fail for having invalid cookies.
Refatored code to check and verify the domain for a particular cookie.

No need to have the code loop through the mimic cookies twice; instead,
check for and update the domain of a cookie the first (and only) time
through. If the user does not call verifyCookieDomainWhenDownloading or
verifyCookieDomainWhenCheckingStatus, then the domain checking/setting
is skipped. This code fixes the isues I had with IE webdriver "loosing"
the domain portion of cookies.

Limitation: Only works for one cookie per download/urlChecker object.
Other: The code is basically duplicated between the two classes. I
did this to keep things in alignment with the original codebase. However,
this could be refactored to pull the reusable bits and have them only
in one place, not two.
Merge pull request #2 from XDelphiGrl/DomainCookieIssueIE

FileDownloader and UrlStatusChecker: Add Methods to Verify and Set Cookie Domain