Hide radio buttons and give their labels the appearance of buttons.

This is done to reduce the amount of screen space used.
Handle inconsistent columns in CSV files.
Fix broken --go option.
Turn SpectrumTypeStub into a ValueType.
No such type as 'Error' in Python.
Remove all unused variables and imports, and other no-op code, according to Pylint and flake8.

more unused code
Add missing abstract method definitions.
Adjust code style based on Pylint and flake8 advice.

* Name unused arguments with _.
* Put all pass statements on separate lines.
* Don't override builtin 'filter' (already trying, missed this one).

formatting
Forward args to top_block.start() in override.
Don't read sys.argv early.
Add configuration files for Pylint and flake8 lint tools; update manual.