8.0.0-rc.3

The same changes were released in 7.2.0 (7.2.0 documentation is actual for this release)

Comparing to previous rc.2:

1. New test field extensions were generalized and now could be also used without junit
2. Base class for annoatted fields extensions was rewritten for simplicity
3. Junit ExtensionContext now could be injected as test method parameter
4. Minor fixes