Enhancements for automated tests

2 enchancements were added to the default engine, in particular for auto tests
* handle a "special" returncode (I chose 69 because it's a bit normalized as "service unavailable" in /usr/include/stdexits.h). The executed script can return 69 to indicate that the test is not available (reasons are multiple: missing binary, test environment detected as incorrect etc.)
* for each testcase: parse the stdout buffer to find a pattern that marks some generated notes from the executed script (pattern is '###[NOTES]###' by default but could be modified easily). For each line matching the pattern, the end of the line (after the pattern) is extracted and concatenated. The final notes buffer is then added to the XML tree as &lt;notes>, direct child of &lt;testcase> (element &lt;notes> is created if not already present in the source tree)