Fix bug when creating contact.
The contact is created asynchronously so we cannot try to get it immediatly.
As a consequence the method IRoster.createContact now return a boolean.
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);
}