UI stop bot shuts down entire application

[Benjamin Cordes]

Shutdownhook has to be bot specific. This is a bit tricky, since it requires separating bot thread from main thread. Shutdownhook contains this line

Thread.currentThread().interrupt();

[Desrever Nu]

beware , in 0.2.0 RC4 Changed shutdown sequence : first terminate all BotTasks, then clear orders, then interrupt mainthread

see changeset https://bitbucket.org/JordanLeePeershares/nubottrading/commits/b3514c7862b4e37635138f2a32680c3de8bb0e22