working extractor ordering. Graylog2/graylog2-web-interface#726
Merge branch '0.20'

Conflicts:
	graylog2-server/src/main/java/org/graylog2/filters/ExtractorFilter.java
	graylog2-server/src/main/java/org/graylog2/rest/resources/system/inputs/ExtractorsResource.java