Support ColumnIndex Attribute

[shps951023]

[shps951023]

https://github.com/shps951023/MiniExcel/pull/144

目前遇到的困難在於 一些使用Index Attribue，一些不用情況
像是

public class Demo
{
            public int MyProperty { get; set; }  //index = 1

            public int MyProperty2 { get; set; } //index = 3
            public int MyProperty3 { get; set; } //index = 4
            [ExcelColumnIndex("A")] // equal column index 0
            public int MyProperty4 { get; set; }
            [ExcelColumnIndex(2)]
            public int MyProperty5 { get; set; } //index = 2
            public int MyProperty6 { get; set; } //index = 5
}

但還在考慮這個功能實不實用，自己沒用過這功能，但其他框架有提供才列在Issue

[shps951023]

        public class Issue142VO
        {
            [ExcelColumnIndex("F")]
            public int MyProperty7 { get; set; } //index = null
        }

[shps951023]

0.11.1

Excel Column Name/Index/Ignore Attribute

e.g

input excel :

public class ExcelAttributeDemo
{
    [ExcelColumnName("Column1")]
    public string Test1 { get; set; }
    [ExcelColumnName("Column2")]
    public string Test2 { get; set; }
    [ExcelIgnore]
    public string Test3 { get; set; }
    [ExcelColumnIndex("I")] // system will convert "I" to 8 index
    public string Test4 { get; set; } 
    public string Test5 { get; } //wihout set will ignore
    public string Test6 { get; private set; } //un-public set will ignore
    [ExcelColumnIndex(3)] // start with 0
    public string Test7 { get; set; }
}

var rows = MiniExcel.Query<ExcelAttributeDemo>(path).ToList();
Assert.Equal("Column1", rows[0].Test1);
Assert.Equal("Column2", rows[0].Test2);
Assert.Null(rows[0].Test3);
Assert.Equal("Test7", rows[0].Test4);
Assert.Null(rows[0].Test5);
Assert.Null(rows[0].Test6);
Assert.Equal("Test4", rows[0].Test7);