port to new soledad async api

**Not ready to merge, missing changes in leap.mail and maybe other to be compatible with the new API**

It needs to synchronize the merge with the soledad async API and the upgrades in leap.mail.
I see I need to rephrase it. The problem is that the constructor of OpenPGPWrapper initialize the indexes in soledad, but don't wait for the deferred to be fired. I did a hack to avoid the problem by adding a method *_wait_indexes* to the wrapper (see https://github.com/meskio/keymanager/blob/feature/6368_async_api/src/leap/keymanager/keys.py#L304) but this only works in the wrapper.

That is why I wanted to add the keyType to this method to move the soledad stuff to the OpenPGPWrapper and be able to wait for the soledad indexes to be ready.