Add restructured text support to wikify an existing sphinx documentation (BB-523)

sphinx has gained wide acceptance as the standard documentation tool for open source python projects. Sphinx just uses text files with a restructured text syntax as source files.

It would be great if bitbucket wiki feature could be able to edit a folder of restructured text files otherwise rendered as a sphinx static site while being wiki editable through the bitbucket web UI or the hg text access.