Document new application property to configure conversion errors displaying

[GlebDurygin]

Relates cuba-platform/cuba#1877

Environment

• Documentation version: 7.2
• Part of the documentation: Manual
• Existing page: Application Properties

Description of the bug or enhancement

Application property cuba.web.conversionErrorDisplayType defines how the conversion errors will be displayed, like exceptions or notifications. The property has two values: EXCEPTION and NOTIFICATION. The default value is EXCEPTION.

[zhenyazb]

wait for cuba-platform/cuba#1877