Doesn't access database directly anymore but goes through AxolotlService
now to obtain list of fingerprints associated with an Account/Contact.
This should prevent orphaned keys littering the UI which previously
couldn't be removed through the Clear Devices function.

Together with 1c79982da84964c1d81179a0927d9cd1eadf53de this fixes #1393

There is no need to preemptively add the keys to the store oneself.
SessionBuilder will take care of this for us. What's more, this will
prevent IdentityKeys from otherwise invalid bundles to show up in our
UI.

If we detect our own ID is not in our own devicelist on receiving an
update, we reannounce ourselves. This used to have the side effect of
modifying the list of devices we thought were in the update set, causing
us to accidentally build a session with ourselves.

This lead to our own key being set to TRUSTED_INACTIVE, resulting in red
lock icons on messages sent by the own device.

We fix this by having publishOwnDeviceId() operate on a copy of the
original set. This commit also includes a db migration which deletes
sessions with oneself and sets own keys back to TRUSTED.

show an send button instead of the enter key in softkeyboards when enterIsSend and showEnterKey are both set

Fixes #1382

Only aborts when a timeout was received. Error conditions (most notably
item-not-found) are interpreted as no other devices existing.

This reverts commit df86b0fc.

Remove invalid check for result code, which prevented publishing if the
node was empty to begin with.

Fix pepBroken check

If PEP publish tries are repeatedly triggered by empty PEP updates, stop
attempting to publish after 3 tries. This should work around broken PEP
implementations in older ejabberd and OpenFire versions.

remove unused imports.