Add more space to "Show system pages" in sitemap

- Allow long texts for "Show system pages"
- Simplify the code (remove the useless `ccm-show-all-pages` div)


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Before:

![sitemap-before](https://f.cloud.github.com/assets/928116/1350040/5781edca-3702-11e3-8fb0-cb0295fbe591.png)

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After:

![sitemap-after](https://f.cloud.github.com/assets/928116/1350041/5e185e58-3702-11e3-98f6-f9e8767a80c3.png)