Add configuration option to disable matchers

[j-hellenberg]

This pull request adds the ability to disable first line matchers in the configuration file, which we found quite useful because our state-of-the-art matchers can be fairly long-running and we don't want to execute all of them in all cases.

[avielhauer]

Thanks for the PR, #11 should help with the problem. To select a set of first-line matchers to be cached, you need to enable writeCacheFirstLineMatchers, adjust first_line_matchers.yaml and first_line_tokenizers.yaml to your liking, run Schematch and then revert the changes to first_line_matchers.yaml and first_line_tokenizers.yaml.

I might later also merge this PR to complement the current caching approach.