Use reified type parameter for executeCatching; sync / async handlers

The unsafe cast before would throw an exception if any other generic
parameter than `Exception` was used without passing the class reference
explicitly.

It can now also be specified whether the exception handler is to be
executed sync or async, defaulting to sync.

src/main/kotlin/net/axay/kspigot/runnables/KSpigotRunnables.kt

@@ -104,6 +104,14 @@ fun task(
 
 }
 
+fun runTask(sync: Boolean, runnable: () -> Unit) {
+    if (sync) {
+        sync(runnable)
+    } else {
+        async(runnable)
+    }
+}
+
 /**
  * Starts a synchronous task.
  */