Added Maven profile ``retryFlakyTests`` to reduce spurious test failures

Use the Maven profile ``retryFlakyTests`` for being robust against tests that
are known to be flaky. Inside Eclipse, you can achieve the same by passing the
system property ``-DretryFlakyTests=true``.

This profile should only be used by the Scala/IDE integration script to avoid
failing because of flakiness in our regression suite.