Invocation Filter Integration

We've added Invocation Filters to the core SDK (https://github.com/Azure/azure-webjobs-sdk/issues/980). This issue tracks integrating that into Functions so filters can be used across languages.

Function Filters can be used in Azure Functions today in scenarios where you're using our VS tooling to deploy precompiled functions to your Function App. In that case you can simply apply filter attributes to your functions and they'll run at the right time in the invocation pipeline. However this doesn't currently work for csx functions that are compiled on the fly (i.e. the standard portal edit experience).