add form component

1. 常规表单
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![image](https://cloud.githubusercontent.com/assets/4003066/5518075/8a50ad28-894e-11e4-82f7-68d05d646057.png)

2. 单行表单
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![image](https://cloud.githubusercontent.com/assets/4003066/5518077/a7063e42-894e-11e4-8b45-3e0acb59c12f.png)

3. 行内表单
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![image](https://cloud.githubusercontent.com/assets/4003066/5518083/e654c2d0-894e-11e4-9ecb-99a38e64ebf7.png)