Remove AutoCode attribute [DefaultValue("+")]

[bantolov]

If web application sends this deafault value to the Rhetos server, then we cannot use the DefaultValue concept in the DSL script to define a different autocode format.

This MVC attribute is not needed, because if an empty value is sent to Rhetos server, the code will be generated with "+" pattern by default.

[bantolov]

Possible workaround: Override the property's attribute for this generated partial class in a new cs file. The override should be [DefaultValue("")].