Added Wizard controller
- Added abstract class StepController
- WelcomeController inherits from PMStepController
- Added order method
Property for active wizard step
Added title label
Added navigation buttons
Can show Wizard view
Can show welcome view
- Bound input fields on welcome page to controller properties
- Added isValid method to StepController
Added validation methods
can switch between steps
Bounds checking for navigation between steps
Added WizardContext and pass it to every step
- PMAccountServerViewController functions as base class for IMAP and
  SMTP settings
- Added SMTP settings class
Show current step's title on top
Bound connection popup button to connection types array
- Removed order method
- Added Vendor view and controller
Added AccountDefaults and AccountDefaultsManager
Replaced magic strings with constants
- Renamed PMAccountVendorXXX to PMAccountProvider
- Bound Account provider list to dictionary
Bind to array of account providers to keep sorting