Fixed: CFHTTPRequest now accepts the withCredentials property

From the original PR:

Currently, CPURLConnection has no way to access the withCredential
property of an XMLHTTPRequest, meaning we can't utilize cross-domain
calls using CORS in our applications.

This commit adds the withCredentials property to CFHTTPRequest.

Refs #1296
Fixed: CPURLConnection now accepts withCredentials

From the original PR:

CPURLConnection was modified to reduce the withCredentials flag to a file-scope member. This has been done to facilitate use of withCredentials when a developer cannot modify the CPURLConnection manually (e.g. https://github.com/wireload/Ratatosk/blob/master/WLRemoteLink.j, line 466).

Refs #1296, #2138
Working #2144: Reintegrated changes from #2138 and fixed test fail.

Now using instance variables for withCredentials.  Also fixed test failure.
Fixed: change variable name

Changed "returnValue" to "connection" - more descriptive.

Ref: https://github.com/cappuccino/cappuccino/pull/2144#commitcomment-6769088
Formatting: Cleaning up CPURLConnection

Removed some extra whitespace and added a newline at the end of the file.
Merge branch 'fix-cfhttp-cpurl-2141-2138' of github.com:ahankinson/cappuccino into fix-cfhttp-cpurl-2141-2138
Formatting: CPURLConnection
Tests: Updating test for CPURLConnection

This test checks to make sure the CPURLConnection withCredentials functionality works.
Test: New CFHTTPRequest test

This commit adds a new test for CFHTTPRequest, which at present only contains the test for withCredentials
Merge branch 'fix-cfhttp-cpurl-2141-2138' of https://github.com/ahankinson/cappuccino into ahankinson-fix-cfhttp-cpurl-2141-2138