* Add check for duplicate adapt intents

There are two cases, duplicated named intent and duplicated anonymous intent.

A named intent will cause a ValueError exception notifying the skill
author that there is a collision.

An anonymous intent will silently derive a new name and use that
instead of the default generated one.

* Add tests for intent collisions

* Make enable/disable intent handle the new exception

The enable/disable intent did not mark an intent as detached, instead it
remained in the list of intents after disabling in the IntentServiceInterface
to be retrieved when the intent should be re-enabled.

This moves detached intents into a list of detached intents to so they
won't cause the double enable exception.

* Add move logic to find if intent is detached

MycroftSkill.enable_intent() will now check if the intent is detached
before trying to re-enable it.

* Lock updates of intents

This should avoid some race conditions that may occur if multiple
threads tries to enable / disable intents