add automatic database setup

requires create-settings.sql and create-schema.sql in same directory as
exe
add error dialog in MainWindow
add setup project
add icon to top left corner
fix only one installfile
add AutoCompleteEntries on refresh
fix not setting currentTabIndex in MainWindow
change autoCompleteEnties to IParty

Fixes flaw which would not add a Customer to AutoCompleteTextBox if a
Supplier with the same name had already been added
refactor BookingsUserControl
fix updating a PaymentRule
refactor SuppliersUserControl
refactor SuppliersUserControl again
fix New button in SuppliersUserControl
Add register singleton for suppliers and customers
load Customers before Suppliers
fix Models so they use Register
prettify Register
add database sql files
register newly created Suppliers and Customers
fix new Customers not added to PaymentRules ACTBox