refactored filter service

- I wasn't too happy with that in the end.
- The filter editor should not be concerned about managing filter rule state.
- Therefore, it should not access a service for filter rules.
- The editor should simply be given a set of rules, and edit that rule set.
- The only entity that should manage filter state should be the document list service, and the saved view service in the form of filters associated with saved views.

src-ui/src/app/components/document-list/document-list.component.html

@@ -63,7 +63,7 @@
 </app-page-header>
 
 <div class="w-100 mb-4">
-  <app-filter-editor [(filterEditorService)]="filterEditorService" (apply)="applyFilterRules()" (clear)="clearFilterRules()" #filterEditor></app-filter-editor>
+  <app-filter-editor [(filterRules)]="list.filterRules" #filterEditor></app-filter-editor>
 </div>
 
 <div class="d-flex justify-content-between align-items-center">