Re-run tests with menu instead of automatically

Don't re-run all tests in OnResume because they all re-run when returning from details activity.
This can cause problems if they were still running from the first time, especially since the list was cleared.
Other changes:
 - Separate custom views into classes
 - Simplify error alert code
 - Asserts from NUnitLite 0.7
 - Add a second test fixture to the example