Eliminate status loop's metric argument dependency

The status loop should only be dependent on repository it ought to be
watched and not the metric. Hence, this commit making it more general.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add tokenizer to metric class and filter to worker

Another approach for a word tokenizer was added to the metric class.
For the Aspell library it is important that attached characters like
periods, commas, brackets, etc. are filtered. So far it looks like a
better approach to test spelling is not to check against every word,
but to check against a list of common spelling mistakes.

This commit is also accompanied by a NaN filter of the final score.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>