Implements a ping listener from XEP-0199 XMPP ping.
In the future, we can send an XMPP ping to the server to check for the state
of the connection.
package net.java.otr4j;
public interface OtrKeyManagerStore {
public abstract byte[] getPropertyBytes(String id);
public abstract boolean getPropertyBoolean(String id, boolean defaultValue);
public abstract void setProperty(String id, byte[] value);
public abstract void setProperty(String id, boolean value);
public abstract void removeProperty(String id);
}