[Form] Improved debugger icon

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

Changes the form icon in the toolbar to be pixel perfect. 

| before                                                                                               | after                                                                                               |
| ---------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------- |
| ![before](https://f.cloud.github.com/assets/890645/1558707/8c4e2d42-4fa4-11e3-9397-376f761869a2.png) | ![after](https://f.cloud.github.com/assets/890645/1558708/90257844-4fa4-11e3-8a83-73d163d47261.png) |