[#1132] Update sphinx builder.

Problem
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Right now, brink only support building sphinx documentation with a hardcoded 'standalone' theme.
We want to build documentation in both standalone and website friendly format.

Changes
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 Moved sphinx spcific things into sphinx module.
Renamed to sphinx and force absolute imports.

How to test
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reviewers: @alibotean 

this is here just to let you know about the changes.

I will use this package in server and you can see the results there :) 

Thanks!