jamiaccount: improve vCard synchronization

Because of the ConnectionManager, the daemon is now able to send
direct messages such as typing indications and read status. This
can be also used to move current features and improve it.

This patch is a first step to improve vCard syncing. The idea is
to send the vCard directly when a peer is connected. To avoid to
send the vCard everytime, a state is written in the cache directory.

In the future, a method to update the vCard as soon as the client
updates its profile will be possible.

Change-Id: I3801cbe04b3441f67ea6685aa2047e5a545958e5