Add support for scalafx in coinffeine-gui module
Introduce hello world like screen for the GUI
Merge pull request #166 from sortega/feature/gui

Introduce scalafx GUI
Add amount validation for currencies
Switch to javafx 8 and use scalafx instead of FXML
Introduce a wizard at application start
Merge pull request #167 from sortega/task/40_wizard

Add wizard support to coinffeine-gui
Merge pull request #165 from edrevo/add-currency-amount-validation

Add amount validation for currencies
Update topmost README file
Simplify `MessageForwarding` entity

So far, `Messageforwarding` has been a trait that requires a
`ExchangeInfo` and a `MessageGateway` provided by its children. It
is used by actors collaborating in the exchange to simplify the
message forwarding.

There is no good reason to use inheritance there. As there is no
good reason to couple the message forwarding to the `ExchangeInfo`
object.

This change turns the trait into a regular class, which receives
the counterpart and the broker connections from its constructor. Now
`MessageForwarding` can be used by composition rather than inheritance.
Merge pull request #168 from sortega/task/readme

Update topmost README file
Add Graphviz directory in doc/ with an initial actor supervision graph
Merge pull request #170 from apoloval/doc/graphviz

Add Graphviz directory in doc/ with an initial actor supervision graph
Merge pull request #169 from apoloval/task/39

Simplify `MessageForwarding` entity
Simplify wizard step interface
Allow wizard steps to disable the “next” button
Implement PasswordStepPane
Merge pull request #171 from sortega/task/40_wizard_steps

Implement PasswordStepPane