Add execution context for updating ScalaFX nodes
Add CredentialsTester trait
Implement OKPayCredentialsStepPane
PR feedback
Merge pull request #172 from sortega/task/40_wizard_steps

Implement OKPayCredentialsStepPane
Generate QR code images
Implement TopUpStepPane
Make the wizard a non-resizable dialog
Move dependencies out of the constructor in the exchange classes
Merge pull request #174 from sortega/task/40_wizard_steps

Implement TopUpStepPane
Merge pull request #173 from edrevo/remove-constructor-deps

Move dependencies out of the constructor in the exchange classes