Don't set `differential.whitespace-matters`.

I don't want to overwrite the default value.
Added `differential.show-test-plan-field` to configuration template.
Fix default value for `differential.require-test-plan-field`.
Add header comments to configuration template.
Add `phd.start-taskmasters` to configuration template.
Fix default values for `syntax.filemap` configuration.
Log output from `phd-launch`.