feat: support [Column]

[DeagleGross]

Goal:

Support [System.ComponentModel.DataAnnotations.Schema.ColumnAttribute] as an additional way to override parameter name.
Requested by some users (stackoverflow)

Example:

To make override work, one need to specify both [Column] and [UseColumnAttribute] attributes, for example:

class MyType
{
    [UseColumnAttribute]
    [Column("myOtherName")]
    public string Name { get; set; }
}

Rules:

1. If [Column] and either [UseColumnAttribute] or [UseColumnAttribute(true)] is defined, than override will work
2. If [UseColumnAttribute(false)] is explicitly specified, then overriding will not happen
3. If [Column] is specified, but [UseColumnAttribute] is missing, then DAP043 will be emitted to the user: "Attach the [UseColumnAttribute] attribute to make Dapper consider [Column]"
4. If 1) is followed, but also [DbValue] with property Name is specified, then a warning message will be emitted to the user: DAP042 "A column name is specified via both [DbValue] and [Column]; '<dbvalue_name>' will be used"

Closes #36

[mgravell]

what is the allowed usage here? can it be applied at the module level, or is it only respected when attached to the same type? are more than one allowed? can we add [AttributeUsage(...)] here accordingly

[DeagleGross]

added such an expression.
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]

let me know if such AttributeUsage is correct

[mgravell]

looking good; fixed some minor nits:

• avoid /en-us/ in docs links; if you cut it, it will use the user's locale settings
• formatting in docs
• used a different variant of that string equality fix

an open question on the new attribute, but: looking good!

[DeagleGross]

looking good; fixed some minor nits:

• avoid /en-us/ in docs links; if you cut it, it will use the user's locale settings
• formatting in docs
• used a different variant of that string equality fix

an open question on the new attribute, but: looking good!

Thanks for the useful advices and fixes, Marc! Sorry for attribute usage - I added it. Ready for review