Add topics for Galaxy and Beacon. Update QC topic.

[deflaux]

• Fixes https://github.com/googlegenomics/readthedocs/issues/102 @bryeung and @mfiume please take a look at Beacon
• Fixes https://github.com/googlegenomics/readthedocs/issues/103 @kellrott please take a look at Galaxy
• Fixes https://github.com/googlegenomics/readthedocs/issues/104 @cuiping and @gregmcinnes please take a look at QC

Please feel free to add more to these topics and edit/correct. Just click on "Edit on GitHub" in the upper right hand corner of the page on readthedocs and send a pull request, thanks!

[mbookman]

Just a few nits, but otherwise good. Please take a look through the overall diff for all the places that the page titles have changed and match up the length of the "====". I know it is not a strict technical requirement, but nice to keep consistent.

[mfiume]

Beacon section looks great, thanks @deflaux.