'Stop on coverage achieved' TestSvm option

[mxprshn]

Added new option for TestSvm attribute: if it is set to true, execution stops when exprectedCoverage is achieved

Implementation details:

• Statistics calculates approximate coverage as covering steps / total instructions count
• Approximate coverage is checked on each .vst test generated. If it is desired, dotCover runs on generated tests. If dotCover shows desired coverage as well, test execution is stopped
• TestResultsChecker was updated to run incrementally: it it has already been run on some tests, and there are some new tests added, dotCover will be run only for them, and then results will be merged with previous

[mxprshn]

It is better to implement this feature with coverage by tests statistics