event log: simplify styles, prevent horizontal scrolling

sql logger: clip context length to 8kb

css/dijit_basic.less

@@ -132,7 +132,7 @@
 
 		.dijitTreeRow {
 			overflow: hidden;
-			-moz-user-select: none; /* TODO: temporary workaround for bug: https://discourse.tt-rss.org/t/is-it-possible-to-create-a-hierarchy-of-categories/876/13 */
+			-moz-user-select: none;
 			text-overflow: ellipsis;
 		}