(#91) Defer throwing exceptions on test failures

[AdmiringWorm]

Description Of Changes

This commit updates the tasks for running unit/integration tests to add an OnError handler so the actual throwing of the exception can be defered to after we have uploaded the test results to any build servers, or when generating local coverage files.

Additionally the unit and coverage results generation continues with any additional tasks if one of these fails.

Motivation and Context

To have test status and coverage reports available even if one or more tests fail.

Testing

1. Tested by copying the files over to the chocolatey/choco tools directory.
2. Run the build.
3. Ensure success
4. Edit one of the tests to throw an exception (or at least fail)
5. Run the build again
6. Ensure build doesn't fail until after the Test task is running.

Change Types Made

• [x] Bug fix (non-breaking change)
• [ ] Feature / Enhancement (non-breaking change)
• [ ] Breaking change (fix or feature that could cause existing functionality to change)
• [ ] PowerShell code changes.

Related Issue

Fixes #91

Change Checklist

• [ ] Requires a change to the documentation
• [ ] Documentation has been updated
• [ ] Tests to cover my changes, have been added
• [ ] All new and existing tests passed.
• [ ] PowerShell v2 compatibility checked.

[gep13]

@AdmiringWorm thanks for getting this added!