Changes to xADDomainTrust

- Refactored the resource to enable unit tests, and at the same time changed
  it to use the same code pattern as the resource xADObjectEnabledState.
- Added unit tests (issue dsccommunity#324).
- Added comment-based help (issue dsccommunity#337).

CHANGELOG.md

@@ -5,6 +5,10 @@
 - Changes to xActiveDirectory
   - Added a Requirements section to every DSC resource README with the bullet point stating "Target machine must be running Windows Server 2008 R2 or later" ([issue #399](https://github.com/PowerShell/xActiveDirectory/issues/399)).
   - Added 'about_\<DSCResource\>.help.txt' file to all resources ([issue #404](https://github.com/PowerShell/xActiveDirectory/issues/404)).
+  - Added new helper functions in xActiveDirectory.Common.
+    - New-CimCredentialInstance
+    - Add-TypeAssembly
+    - New-ADDirectoryContext
 - Changes to xADManagedServiceAccount
   - Added a requirement to README stating "Group Managed Service Accounts need at least one Windows Server 2012 Domain Controller" ([issue #399](https://github.com/PowerShell/xActiveDirectory/issues/399)).
 - Changes to xADComputer
@@ -15,6 +19,11 @@
   - Fixes exception when creating a user with an empty string property ([issue #407](https://github.com/PowerShell/xActiveDirectory/issues/407)).
   - Fixes exception when updating `CommonName` and `Path` concurrently ([issue #402](https://github.com/PowerShell/xActiveDirectory/issues/402)).
   - Fixes ChangePasswordAtLogon Property to be only set to `true` at User Creation ([issue #414](https://github.com/PowerShell/xActiveDirectory/issues/414)).
+- Changes to xADDomainTrust
+  - Refactored the resource to enable unit tests, and at the same time changed
+    it to use the same code pattern as the resource xADObjectEnabledState.
+  - Added unit tests ([issue #324](https://github.com/PowerShell/xActiveDirectory/issues/324)).
+  - Added comment-based help ([issue #337](https://github.com/PowerShell/xActiveDirectory/issues/337)).
 
 ## 3.0.0.0