Missed the Help docs on last commit

Add basic (like, really, really basic docs) on cleaning file and database caches,
caching EMS prereqs.

lib/WebGUI/Help/Workflow_Activity_CacheEMSPrereqs.pm

@@ -0,0 +1,23 @@
+package WebGUI::Help::Workflow_Activity_CacheEMSPrereqs;
+
+our $HELP = {
+	'cache ems prereqs' => {
+		title => 'topicName',
+		body => 'cache ems prereqs body',
+		isa => [
+			{
+				namespace => "Workflow_Activity",
+				tag => "add/edit workflow activity"
+			},
+		],
+		fields => [
+		],
+		variables => [
+		],
+		related => [
+		],
+	},
+
+};
+
+1;  ##All perl modules must return true