* Enhanced InputNumber props with HTMLInputElement attributes.
It is possibile to use additional props supported by the inner input
element:
```
const inputEl = <InputNumber autoFocus />
```
Before this commit the type checker did not recognize the `autoFocus`
prop.
Some attributes must be omitted because they conflict with props
defined on `InputNumberProps` interface
* Renamed type
Probably they conflicts with a reserved name?
@see https://travis-ci.org/ant-design/ant-design/jobs/381668406
> components/input-number/index.tsx(9,93): error TS4022: 'extends' clause of exported interface 'InputNumberProps' has or is using private name 'OmitAttributes'.
* Replace InputNumber onKeyDown typing with the typed one.
Extending HTMLInputElement attributes the `onKeyDown` props now have a
better typing.
For example before this commit accessing to the event `key` attribute resulted
in a type error.
@see https://reactjs.org/docs/events.html#keyboard-events
* Exporting type OmitAttrs on InputNumber component.
This is an attempt to solve the ci error:
> components/input-number/index.tsx(9,93): error TS4022: 'extends' clause of exported
> interface 'InputNumberProps' has or is using private name 'OmitAttrs'.
@see https://travis-ci.org/ant-design/ant-design/jobs/381678316
4077ffb58c