Currently, functional test cases can either pass or fail. There are
occasions when it is helpful to skip tests, for example if the
system they are running on does not meet the requirements for the test.
The rest of the test suite can run without being marked as a failure.
This commit adds framework for tests to skip if their requirements
aren't met.
This commit adds a tool for combining log files from multiple instances
of bitcoinds as well as the test_framework.log file. This gives a
combined view of what the test framework and all bitcoin instances were
doing during a qa test.
