done:
+ master.sql as resource
+ implemented incremental database changes also for Master
+ dbUp sql script variables implemented
+ improved database handling and creation code
+ simpified database creation
+ almost all Database and Tenant creation moved to DatabaseManager.cs (rest code marked with TODO)
+ Unattended install of master can be performed by settings in appsettings.json
+ Improved IsInstalled checking
+ Removed DBSchema field from Tenant
+ Default database and site creation moved to Program.Main
