Instead of relying solely on method names to resolve mappings, it would be beneficial to support explicit mapping names.

[AttributeUsage(AttributeTargets.Method)]
public class NamedMappingAttribute : Attribute
{
    public NamedMappingAttribute(string name);
}

These names should be usable in:

• MapValueAttribute.Use
• MapPropertyAttribute.Use
• MapPropertyFromSourceAttribute.Use
• IncludeMappingConfigurationAttribute.Name

Follow up of #513 / #1833.