Add integration tests for default config #45

They show that an additional report.xml file is generated in both
SmartBear and maven-soapui-extendsion-plugin implementations
Add a test where junitHtmlReport is true #45
Improve junitHtmlReport integration tests #45

Generate report in a subdirectory + check regular test suite junit xml
file existence.
Do not generate html report if configured #45
Remove exception print stack trace (use logger only)