This fixes spopovic/uSiteBuilder#15

[VladimirLevchuk]

• DataTypeAttribute updated to work with v7 PropertyEditorAlias-based model
• UmbracoCore.7.0.0 libraries used
• .NET Framework retargeted to v4.5 to use Umbraco v7.0.0

[VladimirLevchuk]

I fixed target framework for test projects, but I use my company project for testing. uSiteBuilder test sites do not use nuget packages and cannot be easily run in my environment.

Sample code for data type:

[DataType(Name = CustomEditors.SingleLinkPicker
    , PropertyEditorAlias = "RJP.MultiUrlPicker"
    , DataTypeDatabaseType = DataTypeDatabaseType.Nvarchar)]
public class SingleLinkPicker : DataTypeBase
{
    public override DataTypePrevalue[] Prevalues
    {
        get
        {
            return new []
            {
                new DataTypePrevalue("minNumberOfItems", null), 
                new DataTypePrevalue("maxNumberOfItems", "1")
            };
        }
    }
}

[DataType(Name = CustomEditors.MultiMediaPicker
    , PropertyEditorAlias = "Umbraco.MultipleMediaPicker"
    , DataTypeDatabaseType = DataTypeDatabaseType.Nvarchar)]
public class MultiMediaPicker : DataTypeBase
{
    public override DataTypePrevalue[] Prevalues
    {
        get
        {
            return new[]
            {
                new DataTypePrevalue("multiPicker", "1")
            };
        }
    }
}

[DataType(Name = CustomEditors.MultiContentPicker,
    PropertyEditorAlias = "Umbraco.MultiNodeTreePicker")]
public class MultiContentPicker : DataTypeBase
{
    public override DataTypePrevalue[] Prevalues
    {
        get
        {
            return new []
            {
                new DataTypePrevalue("startNode", "{    \"type\": \"content\"  }"), 
                new DataTypePrevalue("filter", null), 
                new DataTypePrevalue("minNumber", null), 
                new DataTypePrevalue("maxNumber", null), 
            };
        }
    }
}