[git] rename the basic old deprecated test class to free the name
[git] Extract GitPlatformTest from GithubTest to reuse in some git tests
[git] convert GitLightTests to be GitPlatformTest
[git] Remove some obsolete not very good test
[git] Fix GitConfigTest: convert from testng, cleanup
[git] remove some unused test utils
[git] Fix GitLogParserTest
[git] Convert & fix GitHistoryUtils test

* Add some handy methods to GitExecutor.
* Prefix command calls with "#" to easier distinguish calls from output.
* Support creating a repo without initial commit.
* Return File from mkdir & touch.
* Introduce overwrite & append in addition to echo, because the latter
  has not clear meaning.
[git & hg tests] support failing in case of non zero exit code
[git] more GitHistoryUtilsTest fixes
Fix GitScenarios: suppress non-zero exit code exception
[git tests] fix some strange Groovy error
[git] remove some obsolete tests
[git] convert & fix GitMergeTest
[git] rename test to what it actually tests
[git] remove some obsolete test
[git] Fixing GitRebaserReorderCommitsTest
[vcs tests] remove code duplication: move some methods to VcsTestUtil
[vcs tests] move some static utility methods to VcsTestUtil
remove unused