Instrumentation tweaks

Below are a list of most changes in this pull request.

### Adds the following:

* log subscriber
* automatic metriks integration
* gate_name to payload for feature_operations
* operation and adapter_name to payload for adapter_operations
* operation, gate_name and feature_name to payload for gate_operations

### Changes the following:

* removes disabled? method, just use enabled?
* event names and namespaces; there are now three (feature_operation|gate_operation|adapter_operation).flipper
* no longer using throw/catch for boolean gate
* boolean toggle now always returns true or false for value
* Toggle #enable and #disable always return true, someday they may return false for failed operations

### Bug fixes

* boolean toggle now smarter about true/false ie: the string false is now false, works similar to ActiveRecords truthiness for boolean columns
* gates now default to the instrumenter of their feature