Asynchronous plugins are handled as though they were synchronous

[TomMalow]

XrmMockup currently handles asynchronous plugins as though they where synchronous which means that the execution order between plugins is incorrect if asynchronous is involved.

Say that a synchronous plugin triggers two other plugins one asynchronous with the execution order 1 and another synchronous plugin with the execution 2. Then normally, the synchronous plugin should run first and there after the asynchronous. However, mockup does the opposite.

[misoeli]

Probably needs #186 before this can be implemented.