Add support for UseDefaultCredentials Option

[LukeWage]

Allow Integrated Windows Authentication to be used when authenticating
to the Exchange server.

I apologize in advance if any part of this pull request is improper. I am very inexperienced with Online Collaboration. I considered creating a JUnit test for the new functionality but I didn't know how I could test the code without a server to contact. I tried to minimize the impact of this code so it only affects users who have enabled the UseDefaultCredentials feature. I disabled it by default to mirror the .NET API.

[azurecla]

Hi @LukeWage, I'm your friendly neighborhood Azure Pull Request Bot (You can call me AZPRBOT). Thanks for your contribution!

In order for us to evaluate and accept your PR, we ask that you sign a contribution license agreement. It's all electronic and will take just minutes. I promise there's no faxing. https://cla.azure.com.

TTYL, AZPRBOT;

[codecov-io]

Current coverage is 10.42%

Merging #517 into master will decrease coverage by -0.01% as of cac2222

@@            master    #517   diff @@
======================================
  Files          550     550       
  Stmts        20436   20442     +6
  Branches      2626    2629     +3
  Methods          0       0       
======================================
  Hit           2132    2132       
- Partial        153     154     +1
- Missed       18151   18156     +5

Review entire Coverage Diff as of cac2222

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[azurecla]

@LukeWage, Thanks for signing the contribution license agreement so quickly! Actual humans will now validate the agreement and then evaluate the PR.

Thanks, AZPRBOT;