Plugin hooks (#1452)

* Refactor session and plugin code
* Add context to job tasks
* Show hooks in plugins page
* Refactor session management

pkg/plugin/examples/js/js.js

@@ -11,6 +11,8 @@ function main() {
             doLongTask();
         } else if (modeArg == "indef") {
             doIndefiniteTask();
+        } else if (modeArg == "hook") {
+            doHookTask();
         }
     } catch (err) {
         return {
@@ -207,4 +209,9 @@ function doIndefiniteTask() {
     }
 }
 
+function doHookTask() {
+    log.Info("JS Hook called!");
+    log.Info(input.Args);
+}
+
 main();