Fixed bug in IE

Fixed bug in IE
Merge branch '3.0.2' of https://github.com/ecomfe/esui into 3.0.2
Used css to set default value insead of inline style

Used css to set default value insead of inline style
Added group functions to ViewContext
Added validity style to textarea
Fixed group issue
Removed skin

Removed skin
Fixed an issue where element is not found when painter accepts null as element id
Changed to treat empty string as valid for some rule
Added MinLength rule
Added a parameter to control event firing

Added a parameter to control event firing
Added an interface to allow resize dialog by hand

Added an interface to allow resize dialog by hand
Removed redundant spaces

Removed redundant spaces
Forbidden to use stacking class

Forbidden to use stacking class to enhance hereditability
Added disabled state class

Added disabled state class
Fixed a bug
更改BoxGroup控件中，checked属性的判断方式，以解决firefox下的兼容问题
Added scalability method
Fixed a deep-core bug

We should compare a property's new value from its old value, but
retrieving old value should enable **getter**s, so use `this.get(key)`
instead of `this[key]`
Provided methods to enable/disable single item in BoxGroup

Fixed #147