Database Manager

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

Oqtane.Server/Repository/TenantRepository.cs

@@ -49,10 +49,14 @@ namespace Oqtane.Repository
         }
 
         public void DeleteTenant(int tenantId)
-        { 
+        {
             Tenant tenant = _db.Tenant.Find(tenantId);
-            _db.Tenant.Remove(tenant);
-            _db.SaveChanges();
+            if (tenant != null)
+            {
+                _db.Tenant.Remove(tenant);
+                _db.SaveChanges();
+            }
+
             _cache.Remove("tenants");
         }
     }