beego/context: Fix ignored Header in case SetStatus has been called before

Generate default value while run ORM cmd tool

Makes RenderForm use textarea-element when form type is `textarea`

beego: fix #657

When RenderForm encounters a field with the structTag `form` value
type `textarea` it renders an actual <textarea> html tag.

Extracted a func `parseFormTag` that takes a reflect.StructField
and returns the different positional parts of the `form` structTag
with default values as documented in
http://beego.me/docs/mvc/view/view.md#renderform

This makes RenderForm shorter and makes it possible to test the
parsing separately.

路由地址不区分大小写问题

* not match the empty route

ignore nil time

update chat example