qt: show all units in send confirmation

Make users accustomed to the other subdivision units (mBTC, muBTC) by showing the total amount in all units in the confirmation dialog.

This was recently raised on the mailing list and could be a preparation for switching over the default unit eventually.

![allunits](https://f.cloud.github.com/assets/126646/1558415/c6f324ae-4f8e-11e3-91ac-88e2705c32db.png)