coafile optimization

[ksdme]

Currently coala runs all the bears specified in .coafile irrespective of whether issues generated by them can be reported back to the editor. Some kind of runtime filtering of such bears could improve performance of the ls.

[gaocegege]

Yhea, while it means that we need to implement a syntax parser or reuse the logic about parsing in coala, IMO. I am not sure if regex could do the filter work.

[ksdme]

We could also mutate the internal state of coala, a hacky solution though. https://github.com/coala/coala/blob/25e019cdd944532f969d5cf1079afd7d62f41e19/coalib/processes/Processing.py#L733