LogAnalyzer: make all subclasses of Test call their parent __init()__ function when overriding that function. This is the way of Python.
LogAnalyzer: Fix indent which I broke when merging.
LogAnalyzer: There is no self.logfile, so this must be self.filename.
LogAnalyzer: Default to automatic log format detection.
LogAnalyzer: Allow instantiation of DataFlashlog with no input filename, for backward compatibility. My changes make m_dflog=DataFlashlog('/path/to/file.log') work, which seems like the preferable way, but we don't want to break backwards compatibility.
LogAnalyzer: Update to include the new "format" argument, and fix scoping on two new tests.